diff --git a/api/v1/_dois/PKPBackendDoiController.php b/api/v1/_dois/PKPBackendDoiController.php
index d96facc7471..6a53e97483b 100644
--- a/api/v1/_dois/PKPBackendDoiController.php
+++ b/api/v1/_dois/PKPBackendDoiController.php
@@ -32,6 +32,8 @@
 use PKP\security\authorization\UserRolesRequiredPolicy;
 use PKP\security\Role;
 use PKP\submission\GenreDAO;
+use PKP\userGroup\UserGroup;
+
 
 class PKPBackendDoiController extends PKPBaseController
 {
@@ -128,9 +130,10 @@ public function editPublication(Request $illuminateRequest): JsonResponse
         $publication = Repo::publication()->get($publication->getId());
 
         $submission = Repo::submission()->get($publication->getData('submissionId'));
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+
+        $contextId = $submission->getData('contextId');
+        $userGroups = UserGroup::withContextIds($contextId)->get();
+
 
         $genreDao = DAORegistry::getDAO('GenreDAO'); /** @var GenreDAO $genreDao */
         $genres = $genreDao->getByContextId($submission->getData('contextId'))->toArray();
diff --git a/api/v1/_submissions/PKPBackendSubmissionsController.php b/api/v1/_submissions/PKPBackendSubmissionsController.php
index 3b54238b4a0..3223804cd7c 100644
--- a/api/v1/_submissions/PKPBackendSubmissionsController.php
+++ b/api/v1/_submissions/PKPBackendSubmissionsController.php
@@ -36,6 +36,8 @@
 use PKP\security\Role;
 use PKP\submission\DashboardView;
 use PKP\submission\PKPSubmission;
+use PKP\userGroup\UserGroup;
+
 
 abstract class PKPBackendSubmissionsController extends PKPBaseController
 {
@@ -218,9 +220,10 @@ public function getMany(Request $illuminateRequest): JsonResponse
 
         $submissions = $collector->getMany();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $contextId = $context->getId();
+
+        $userGroups = UserGroup::withContextIds($contextId)->cursor();
+
 
         /** @var \PKP\submission\GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -253,9 +256,8 @@ public function assigned(Request $illuminateRequest): JsonResponse
             ->assignedTo([$user->getId()])
             ->getMany();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $contextId = $context->getId();
+        $userGroups = UserGroup::withContextIds($contextId)->cursor();
 
         /** @var \PKP\submission\GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -325,9 +327,8 @@ public function reviews(Request $illuminateRequest): JsonResponse
 
         $submissions = $collector->getMany();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $contextId = $context->getId();
+        $userGroups = UserGroup::withContextIds($contextId)->cursor();
 
         /** @var \PKP\submission\GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
diff --git a/api/v1/submissions/AnonymizeData.php b/api/v1/submissions/AnonymizeData.php
index 88ba9551def..cecc5313b49 100644
--- a/api/v1/submissions/AnonymizeData.php
+++ b/api/v1/submissions/AnonymizeData.php
@@ -55,13 +55,12 @@ public function anonymizeReviews(LazyCollection|Submission $submissions, ?LazyCo
             ->pluck('user_group_id')
             ->toArray();
 
-        $currentUserGroups = Repo::userGroup()->getCollector()
-            ->filterByUserGroupIds($currentUserUserGroupIds)
-            ->getMany();
+        $currentUserGroups = UserGroup::withUserGroupIds($currentUserUserGroupIds)->get();
+
 
         $isAuthor = $currentUserGroups->contains(
             fn (UserGroup $userGroup) =>
-            $userGroup->getRoleId() == Role::ROLE_ID_AUTHOR
+            $userGroup->roleId == Role::ROLE_ID_AUTHOR
         );
 
         if ($currentUserReviewAssignment->isNotEmpty() || $isAuthor) {
diff --git a/api/v1/submissions/PKPSubmissionController.php b/api/v1/submissions/PKPSubmissionController.php
index dffbc1bda5f..fb5b446c7e2 100644
--- a/api/v1/submissions/PKPSubmissionController.php
+++ b/api/v1/submissions/PKPSubmissionController.php
@@ -32,6 +32,7 @@
 use Illuminate\Support\Enumerable;
 use Illuminate\Support\Facades\Mail;
 use Illuminate\Support\Facades\Route;
+use Illuminate\Support\LazyCollection;
 use PKP\components\forms\FormComponent;
 use PKP\components\forms\publication\PKPCitationsForm;
 use PKP\components\forms\publication\PKPMetadataForm;
@@ -70,6 +71,7 @@
 use PKP\submissionFile\SubmissionFile;
 use PKP\userGroup\UserGroup;
 
+
 class PKPSubmissionController extends PKPBaseController
 {
     use AnonymizeData;
@@ -425,9 +427,7 @@ public function getMany(Request $illuminateRequest): JsonResponse
 
         $anonymizeReviews = $this->anonymizeReviews($submissions);
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($context->getId())->cursor();
 
         /** @var \PKP\submission\GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -533,9 +533,8 @@ public function get(Request $illuminateRequest): JsonResponse
     {
         $submission = $this->getAuthorizedContextObject(Application::ASSOC_TYPE_SUBMISSION);
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
+
 
         // Anonymize sensitive review assignment data if user is a reviewer or author assigned to the article and review isn't open
         $reviewAssignments = Repo::reviewAssignment()->getCollector()->filterBySubmissionIds([$submission->getId()])->getMany()->remember();
@@ -599,20 +598,20 @@ public function add(Request $illuminateRequest): JsonResponse
                 }
             }
         }
+        $submitterUserGroups = UserGroup::withContextIds($context->getId())
+            ->withRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_AUTHOR])
+            ->whereHas('userUserGroups', function ($query) use ($user) {
+                $query->withUserId($user->getId());
+            })
+            ->get();
 
-        $submitterUserGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->filterByUserIds([$user->getId()])
-            ->filterByRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_AUTHOR])
-            ->getMany();
 
         $userGroupIdPropName = 'userGroupId';
 
         if (isset($params[$userGroupIdPropName])) {
             $submitAsUserGroup = $submitterUserGroups
                 ->first(function (UserGroup $userGroup) use ($params, $userGroupIdPropName) {
-                    return $userGroup->getId() === $params[$userGroupIdPropName];
+                    return $userGroup->id === $params[$userGroupIdPropName];
                 });
             if (!$submitAsUserGroup) {
                 $errors[$userGroupIdPropName] = [__('api.submissions.400.invalidSubmitAs')];
@@ -624,14 +623,14 @@ public function add(Request $illuminateRequest): JsonResponse
                 })
                 ->first();
         } else {
-            $submitAsUserGroup = Repo::userGroup()->getFirstSubmitAsAuthorUserGroup($context->getId());
+            $submitAsUserGroup = UserGroup::withContextIds($context->getId())->withRoleIds(Role::ROLE_ID_AUTHOR)->first();
             if (!$submitAsUserGroup) {
                 $errors[$userGroupIdPropName] = [__('submission.wizard.notAllowed.description')];
             } else {
                 Repo::userGroup()->assignUserToGroup(
                     $user->getId(),
-                    $submitAsUserGroup->getId()
-                );
+                    $submitAsUserGroup->id
+                    );
             }
         }
 
@@ -655,32 +654,34 @@ public function add(Request $illuminateRequest): JsonResponse
         Repo::stageAssignment()
             ->build(
                 $submission->getId(),
-                $submitAsUserGroup->getId(),
+                $submitAsUserGroup->id,
                 $request->getUser()->getId(),
-                $submitAsUserGroup->getRecommendOnly(),
+                $submitAsUserGroup->recommendOnly,
                 // Authors can always edit metadata before submitting
                 $submission->getData('submissionProgress')
                     ? true
-                    : $submitAsUserGroup->getPermitMetadataEdit()
+                    : $submitAsUserGroup->permitMetadataEdit
             );
 
         // Create an author record from the submitter's user account
-        if ($submitAsUserGroup->getRoleId() === Role::ROLE_ID_AUTHOR) {
+        if ($submitAsUserGroup->roleId === Role::ROLE_ID_AUTHOR) {
             $author = Repo::author()->newAuthorFromUser($request->getUser());
             $author->setData('publicationId', $publication->getId());
-            $author->setUserGroupId($submitAsUserGroup->getId());
+            $author->setUserGroupId($submitAsUserGroup->id);
             $authorId = Repo::author()->add($author);
             Repo::publication()->edit($publication, ['primaryContactId' => $authorId]);
         }
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
         $genres = $genreDao->getByContextId($submission->getData('contextId'))->toArray();
 
+        if (!$userGroups instanceof LazyCollection) {
+            $userGroups = $userGroups->lazy();
+        }
+
         return response()->json(Repo::submission()->getSchemaMap()->map($submission, $userGroups, $genres), Response::HTTP_OK);
     }
 
@@ -712,9 +713,7 @@ public function edit(Request $illuminateRequest): JsonResponse
 
         $submission = Repo::submission()->get($submission->getId());
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -766,11 +765,7 @@ public function saveForLater(Request $illuminateRequest): JsonResponse
         Mail::send($mailable);
 
         $submission = Repo::submission()->get($submission->getId());
-
-        $userGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -847,10 +842,10 @@ public function submit(Request $illuminateRequest): JsonResponse
             Repo::eventLog()->add($eventLog);
         }
 
-        $userGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $contextId = $context->getId();
+        $userGroups = UserGroup::withContextIds($contextId)->cursor();
+
+        
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -872,9 +867,8 @@ public function delete(Request $illuminateRequest): JsonResponse
             ], Response::HTTP_NOT_FOUND);
         }
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
+
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1033,9 +1027,7 @@ public function getPublications(Request $illuminateRequest): JsonResponse
 
         $publications = $collector->getMany();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         $currentUserReviewAssignment = Repo::reviewAssignment()->getCollector()
             ->filterBySubmissionIds([$submission->getId()])
@@ -1077,9 +1069,7 @@ public function getPublication(Request $illuminateRequest): JsonResponse
             ], Response::HTTP_FORBIDDEN);
         }
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1117,9 +1107,8 @@ public function addPublication(Request $illuminateRequest): JsonResponse
         $newId = Repo::publication()->add($publication);
         $publication = Repo::publication()->get($newId);
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
+
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1199,9 +1188,7 @@ public function versionPublication(Request $illuminateRequest): JsonResponse
             Mail::send($mailable);
         }
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1275,9 +1262,7 @@ public function editPublication(Request $illuminateRequest): JsonResponse
         Repo::publication()->edit($publication, $params);
         $publication = Repo::publication()->get($publication->getId());
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1337,9 +1322,8 @@ public function publishPublication(Request $illuminateRequest): JsonResponse
 
         $publication = Repo::publication()->get($publication->getId());
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
+
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1381,9 +1365,8 @@ public function unpublishPublication(Request $illuminateRequest): JsonResponse
 
         $publication = Repo::publication()->get($publication->getId());
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
+
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1425,9 +1408,7 @@ public function deletePublication(Request $illuminateRequest): JsonResponse
             ], Response::HTTP_FORBIDDEN);
         }
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($submission->getData('contextId'))->cursor();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -1791,7 +1772,7 @@ public function addDecision(Request $illuminateRequest): JsonResponse
 
     protected function getFirstUserGroupInRole(Enumerable $userGroups, int $role): ?UserGroup
     {
-        return $userGroups->first(fn (UserGroup $userGroup) => $userGroup->getRoleId() === $role);
+        return $userGroups->first(fn (UserGroup $userGroup) => $userGroup->roleId === $role);
     }
 
     /**
@@ -1907,8 +1888,7 @@ protected function getPublicationLicenseForm(Request $illuminateRequest): JsonRe
 
         $submissionLocale = $submission->getData('locale');
         $locales = $this->getPublicationFormLocales($context, $submission);
-        $authorUserGroups = Repo::userGroup()->getByRoleIds([Role::ROLE_ID_AUTHOR], $submission->getData('contextId'));
-
+        $authorUserGroups = UserGroup::query()->withContextIds([$submission->getData('contextId')])->withRoleIds([Role::ROLE_ID_AUTHOR])->cursor();
         $publicationLicenseForm = new PKPPublicationLicenseForm($publicationApiUrl, $locales, $publication, $context, $authorUserGroups);
 
         return response()->json($this->getLocalizedForm($publicationLicenseForm, $submissionLocale, $locales), Response::HTTP_OK);
diff --git a/classes/author/Author.php b/classes/author/Author.php
index 2580825406b..8db937368c3 100644
--- a/classes/author/Author.php
+++ b/classes/author/Author.php
@@ -17,10 +17,9 @@
  */
 
 namespace PKP\author;
-
-use APP\facades\Repo;
 use PKP\facades\Locale;
 use PKP\identity\Identity;
+use PKP\userGroup\UserGroup;
 
 class Author extends Identity
 {
@@ -212,8 +211,8 @@ public function getUserGroup()
     {
         //FIXME: should this be queried when fetching Author from DB? - see #5231.
         static $userGroup; // Frequently we'll fetch the same one repeatedly
-        if (!$userGroup || $this->getUserGroupId() != $userGroup->getId()) {
-            $userGroup = Repo::userGroup()->get($this->getUserGroupId());
+        if (!$userGroup || $this->getData('userGroupId') != $userGroup->id) {
+            $userGroup = UserGroup::find($this->getData('userGroupId'));
         }
         return $userGroup;
     }
@@ -226,7 +225,8 @@ public function getUserGroup()
     public function getLocalizedUserGroupName()
     {
         $userGroup = $this->getUserGroup();
-        return $userGroup->getLocalizedName();
+        return $userGroup ? $userGroup->getLocalizedData('name') : null;
+
     }
 
     /**
diff --git a/classes/author/maps/Schema.php b/classes/author/maps/Schema.php
index 85e793acc8e..4ed4eb18add 100644
--- a/classes/author/maps/Schema.php
+++ b/classes/author/maps/Schema.php
@@ -35,7 +35,7 @@ public function __construct(PKPRequest $request, \PKP\context\Context $context,
     {
         parent::__construct($request, $context, $schemaService);
 
-        $this->authorUserGroups = Repo::userGroup()->getByRoleIds([Role::ROLE_ID_AUTHOR], $this->context->getId());
+        $this->authorUserGroups = UserGroup::withRoleIds(Role::ROLE_ID_AUTHOR)->withContextIds($this->context->getId())->cursor();
     }
 
     /**
@@ -94,8 +94,8 @@ protected function mapByProperties(array $props, Author $item): array
             switch ($prop) {
                 case 'userGroupName':
                     /** @var UserGroup $userGroup */
-                    $userGroup = $this->authorUserGroups->first(fn (UserGroup $userGroup) => $userGroup->getId() === $item->getData('userGroupId'));
-                    $output[$prop] = $userGroup ? $userGroup->getName(null) : new stdClass();
+                    $userGroup = $this->authorUserGroups->first(fn (UserGroup $userGroup) => $userGroup->id === $item->getData('userGroupId'));
+                    $output[$prop] = $userGroup ? $userGroup->name : new stdClass();
                     break;
                 case 'fullName':
                     $output[$prop] = $item->getFullName();
diff --git a/classes/components/forms/context/PKPAppearanceMastheadForm.php b/classes/components/forms/context/PKPAppearanceMastheadForm.php
index b321ec04799..3ffe1d1c4ff 100644
--- a/classes/components/forms/context/PKPAppearanceMastheadForm.php
+++ b/classes/components/forms/context/PKPAppearanceMastheadForm.php
@@ -15,11 +15,12 @@
 
 namespace PKP\components\forms\context;
 
-use APP\facades\Repo;
 use PKP\components\forms\FieldHTML;
 use PKP\components\forms\FieldOptions;
 use PKP\components\forms\FormComponent;
 use PKP\security\Role;
+use PKP\userGroup\UserGroup;
+
 
 class PKPAppearanceMastheadForm extends FormComponent
 {
@@ -42,22 +43,22 @@ public function __construct($action, $locales, $context)
 
         $savedMastheadUserGroupIdsOrder = (array) $context->getData('mastheadUserGroupIds');
 
-        $collector = Repo::userGroup()->getCollector();
-        $allMastheadUserGroups = $collector
-            ->filterByContextIds([$context->getId()])
-            ->filterByMasthead(true)
-            ->filterExcludeRoles([Role::ROLE_ID_REVIEWER])
-            ->orderBy($collector::ORDERBY_ROLE_ID)
-            ->getMany()
-            ->toArray();
-
-        // sort the mashead roles in their saved order
-        $sortedAllMastheadUserGroups = array_replace(array_intersect_key(array_flip($savedMastheadUserGroupIdsOrder), $allMastheadUserGroups), $allMastheadUserGroups);
-
+        $allMastheadUserGroups = UserGroup::withContextIds($context->getId())
+            ->masthead(true)
+            ->excludeRoleIds(Role::ROLE_ID_REVIEWER)
+            ->orderByRoleId()
+            ->get();
+    
+        // Sort the masthead user groups in their saved order
+        $sortedAllMastheadUserGroups = $allMastheadUserGroups->sortBy(function ($userGroup) use ($savedMastheadUserGroupIdsOrder) {
+            return array_search($userGroup->id, $savedMastheadUserGroupIdsOrder);
+        })->values();
+        
+        $mastheadOptions = [];
         foreach ($sortedAllMastheadUserGroups as $userGroup) {
             $mastheadOptions[] = [
-                'value' => $userGroup->getId(),
-                'label' => $userGroup->getLocalizedName()
+                'value' => $userGroup->id,
+                'label' => $userGroup->getLocalizedData('name')
             ];
         }
 
@@ -69,9 +70,9 @@ public function __construct($action, $locales, $context)
             'options' => $mastheadOptions,
             'allowOnlySorting' => true
         ]))
-            ->addField(new FieldHTML('reviewer', [
-                'label' => __('user.role.reviewers'),
-                'description' => __('manager.setup.editorialMasthead.order.reviewers.description')
-            ]));
+        ->addField(new FieldHTML('reviewer', [
+            'label' => __('user.role.reviewers'),
+            'description' => __('manager.setup.editorialMasthead.order.reviewers.description')
+        ]));
     }
 }
diff --git a/classes/components/forms/context/PKPNotifyUsersForm.php b/classes/components/forms/context/PKPNotifyUsersForm.php
index 00be9b088f7..92e06bed3c5 100644
--- a/classes/components/forms/context/PKPNotifyUsersForm.php
+++ b/classes/components/forms/context/PKPNotifyUsersForm.php
@@ -21,6 +21,7 @@
 use PKP\components\forms\FieldRichTextarea;
 use PKP\components\forms\FieldText;
 use PKP\components\forms\FormComponent;
+use PKP\userGroup\UserGroup;
 
 class PKPNotifyUsersForm extends FormComponent
 {
@@ -41,22 +42,21 @@ public function __construct($action, $context)
     {
         $this->action = $action;
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
-
-        $userCountByGroupId = Repo::userGroup()->getUserCountByContextId($context->getId());
+        $userGroups = UserGroup::withContextIds($context->getId())
+            ->withCount(['userUserGroups as userCount'])
+            ->get();
 
         $userGroupOptions = [];
         foreach ($userGroups as $userGroup) {
-            if (in_array($userGroup->getId(), (array) $context->getData('disableBulkEmailUserGroups'))) {
+            $userGroupId = $userGroup->id;
+            if (in_array($userGroupId, (array) $context->getData('disableBulkEmailUserGroups'))) {
                 continue;
             }
             $userGroupOptions[] = [
-                'value' => $userGroup->getId(),
+                'value' => $userGroupId,
                 'label' => $userGroup->getLocalizedData('name'),
             ];
-            $this->userGroupCounts[$userGroup->getId()] = $userCountByGroupId->get($userGroup->getId(), 0);
+            $this->userGroupCounts[$userGroupId] = $userGroup->userCount ?? 0;
         }
 
         $currentUser = Application::get()->getRequest()->getUser();
diff --git a/classes/components/forms/context/PKPRestrictBulkEmailsForm.php b/classes/components/forms/context/PKPRestrictBulkEmailsForm.php
index 9e95895af67..76e12276650 100644
--- a/classes/components/forms/context/PKPRestrictBulkEmailsForm.php
+++ b/classes/components/forms/context/PKPRestrictBulkEmailsForm.php
@@ -38,7 +38,7 @@ public function __construct($action, $context, LazyCollection $userGroups)
         $userGroupOptions = [];
         foreach ($userGroups as $userGroup) {
             $userGroupOptions[] = [
-                'value' => $userGroup->getId(),
+                'value' => $userGroup->id,
                 'label' => htmlspecialchars($userGroup->getLocalizedData('name')),
             ];
         }
diff --git a/classes/components/forms/publication/ContributorForm.php b/classes/components/forms/publication/ContributorForm.php
index f608d4b9e03..66e9e157153 100644
--- a/classes/components/forms/publication/ContributorForm.php
+++ b/classes/components/forms/publication/ContributorForm.php
@@ -48,16 +48,13 @@ public function __construct(string $action, array $locales, ?Submission $submiss
         $this->submission = $submission;
         $this->context = $context;
 
-        $authorUserGroupsOptions = Repo::userGroup()
-            ->getCollector()
-            ->filterByRoleIds([Role::ROLE_ID_AUTHOR])
-            ->filterByContextIds([$context->getId()])
-            ->getMany()
+        $authorUserGroupsOptions = UserGroup::withRoleIds([Role::ROLE_ID_AUTHOR])
+            ->withContextIds([$context->getId()])
+            ->get()
             ->map(fn (UserGroup $authorUserGroup) => [
-                'value' => (int) $authorUserGroup->getId(),
-                'label' => $authorUserGroup->getLocalizedName(),
+                'value' => (int) $authorUserGroup->usergroupid,
+                'label' => $authorUserGroup->getLocalizedData('name'),
             ]);
-
         $isoCodes = app(IsoCodesFactory::class);
         $countries = [];
         foreach ($isoCodes->getCountries() as $country) {
diff --git a/classes/components/forms/statistics/users/ReportForm.php b/classes/components/forms/statistics/users/ReportForm.php
index f1ea56220d2..e731bd5600a 100644
--- a/classes/components/forms/statistics/users/ReportForm.php
+++ b/classes/components/forms/statistics/users/ReportForm.php
@@ -20,6 +20,8 @@
 use PKP\components\forms\FormComponent;
 use PKP\context\Context;
 use PKP\userGroup\UserGroup;
+use PKP\userGroup\Repository as UserGroupRepository;
+
 
 class ReportForm extends FormComponent
 {
@@ -38,21 +40,20 @@ public function __construct(string $action, Context $context)
         $this->addPage(['id' => 'default', 'submitButton' => ['label' => __('common.export')]]);
         $this->addGroup(['id' => 'default', 'pageId' => 'default']);
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds($context->getId())->get();
+
 
         $this->addField(new FieldOptions('userGroupIds', [
             'groupId' => 'default',
             'label' => __('user.group'),
             'description' => __('manager.export.usersToCsv.description'),
-            'options' => $userGroups->values()->map(function (UserGroup $userGroup) {
+            'options' => $userGroups->map(function (UserGroup $userGroup) {
                 return [
-                    'value' => $userGroup->getId(),
-                    'label' => htmlspecialchars($userGroup->getLocalizedName())
+                    'value' => $userGroup->id,
+                    'label' => htmlspecialchars($userGroup->getLocalizedData('name')),
                 ];
-            }),
-            'default' => $userGroups->keys(),
+            })->values()->toArray(),
+            'default' => $userGroups->pluck('id')->toArray(),
         ]));
     }
 }
diff --git a/classes/components/forms/submission/StartSubmission.php b/classes/components/forms/submission/StartSubmission.php
index e8f812bfd04..94e8e77ec09 100644
--- a/classes/components/forms/submission/StartSubmission.php
+++ b/classes/components/forms/submission/StartSubmission.php
@@ -157,12 +157,12 @@ protected function addUserGroups(Enumerable $userGroups): void
         }
 
         $options = $userGroups->map(fn (UserGroup $userGroup) => [
-            'value' => $userGroup->getId(),
-            'label' => $userGroup->getLocalizedName(),
+            'value' => $userGroup->id,
+            'label' => $userGroup->getLocalizedData('name'),
         ]);
 
         $hasEditorialRole = $userGroups->contains(
-            fn (UserGroup $userGroup) => in_array($userGroup->getRoleId(), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN])
+            fn (UserGroup $userGroup) => in_array($userGroup->roleId, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN])
         );
 
         $description = __('submission.submit.availableUserGroupsDescription');
diff --git a/classes/context/SubEditorsDAO.php b/classes/context/SubEditorsDAO.php
index b8b2f1c42b8..5e80e2befce 100644
--- a/classes/context/SubEditorsDAO.php
+++ b/classes/context/SubEditorsDAO.php
@@ -84,8 +84,9 @@ public function deleteEditor(int $contextId, $assocId, $userId, $assocType)
      *
      * @param int[] $assocIds Section or category ids
      * @param int $assocType Application::ASSOC_TYPE_SECTION or Application::ASSOC_TYPE_CATEGORY
+     * @param int $contextId
      *
-     * @return Collection result rows with userId and userGroupId columns
+     * @return \Illuminate\Support\Collection<int, \stdClass> result rows with userId and userGroupId properties
      */
     public function getBySubmissionGroupIds(array $assocIds, int $assocType, int $contextId): Collection
     {
@@ -197,10 +198,9 @@ public function assignEditors(Submission $submission, Context $context): Collect
         // that will cause duplicates to be overwritten
         $assignments = collect($assignments)->mapWithKeys(fn ($assignment, $key) => [$assignment->userId . '-' . $assignment->userGroupId => $assignment]);
 
-        $userGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
+        $userGroups = UserGroup::query()
+            ->withContextIds([$submission->getData('contextId')])
+            ->get();
 
         $userGroupIds = $userGroups->keys();
 
@@ -210,13 +210,13 @@ public function assignEditors(Submission $submission, Context $context): Collect
         });
 
         foreach ($assignments as $assignment) {
-            $userGroup = $userGroups->first(fn (UserGroup $userGroup) => $userGroup->getId() == $assignment->userGroupId);
+            $userGroup = $userGroups->first(fn (UserGroup $userGroup) => $userGroup->id == $assignment->userGroupId);
             Repo::stageAssignment()
                 ->build(
                     $submission->getId(),
                     $assignment->userGroupId,
                     $assignment->userId,
-                    $userGroup->getRecommendOnly()
+                    $userGroup->recommendOnly,
                 );
         }
 
diff --git a/classes/controllers/grid/GridHandler.php b/classes/controllers/grid/GridHandler.php
index 50c62ef9184..c97a03b9550 100644
--- a/classes/controllers/grid/GridHandler.php
+++ b/classes/controllers/grid/GridHandler.php
@@ -399,12 +399,16 @@ public function hasGridDataElements($request)
     public function setGridDataElements($data)
     {
         $this->callFeaturesHook('setGridDataElements', ['grid' => &$this, 'data' => &$data]);
-
+    
         $this->_data = match (true) {
-            $data instanceof Enumerable => $this->toAssociativeArray($data),
+            $data instanceof LazyCollection => $this->toAssociativeArray($data),
+    
+            $data instanceof Enumerable => $this->toAssociativeArray(LazyCollection::make($data)),
+    
             $data instanceof DAOResultFactory => $data->toAssociativeArray(),
             $data instanceof ItemIterator => $data->toArray(),
-            is_iterable($data) => $data
+            is_iterable($data) => $data,
+            default => [],
         };
     }
 
diff --git a/classes/core/PKPApplication.php b/classes/core/PKPApplication.php
index 5e32022c74e..96029082ce2 100644
--- a/classes/core/PKPApplication.php
+++ b/classes/core/PKPApplication.php
@@ -154,7 +154,7 @@ class_alias('\PKP\payment\QueuedPayment', '\QueuedPayment'); // QueuedPayment in
         Hook::addUnsupportedHooks('Mail::send', 'EditorAction::modifyDecisionOptions', 'EditorAction::recordDecision', 'Announcement::getProperties', 'Author::getProperties::values', 'EmailTemplate::getProperties', 'Galley::getProperties::values', 'Issue::getProperties::fullProperties', 'Issue::getProperties::summaryProperties', 'Issue::getProperties::values', 'Publication::getProperties', 'Section::getProperties::fullProperties', 'Section::getProperties::summaryProperties', 'Section::getProperties::values', 'Submission::getProperties::values', 'SubmissionFile::getProperties', 'User::getProperties::fullProperties', 'User::getProperties::reviewerSummaryProperties', 'User::getProperties::summaryProperties', 'User::getProperties::values', 'Announcement::getMany::queryBuilder', 'Announcement::getMany::queryObject', 'Author::getMany::queryBuilder', 'Author::getMany::queryObject', 'EmailTemplate::getMany::queryBuilder', 'EmailTemplate::getMany::queryObject::custom', 'EmailTemplate::getMany::queryObject::default', 'Galley::getMany::queryBuilder', 'Issue::getMany::queryBuilder', 'Publication::getMany::queryBuilder', 'Publication::getMany::queryObject', 'Stats::getOrderedObjects::queryBuilder', 'Stats::getRecords::queryBuilder', 'Stats::queryBuilder', 'Stats::queryObject', 'Submission::getMany::queryBuilder', 'Submission::getMany::queryObject', 'SubmissionFile::getMany::queryBuilder', 'SubmissionFile::getMany::queryObject', 'User::getMany::queryBuilder', 'User::getMany::queryObject', 'User::getReviewers::queryBuilder', 'CategoryDAO::_fromRow', 'IssueDAO::_fromRow', 'IssueDAO::_returnIssueFromRow', 'SectionDAO::_fromRow', 'UserDAO::_returnUserFromRow', 'UserDAO::_returnUserFromRowWithData', 'UserDAO::_returnUserFromRowWithReviewerStats', 'UserGroupDAO::_returnFromRow', 'ReviewerSubmissionDAO::_fromRow', 'API::stats::publication::abstract::params', 'API::stats::publication::galley::params', 'API::stats::publications::abstract::params', 'API::stats::publications::galley::params', 'PKPLocale::installLocale', 'PKPLocale::registerLocaleFile', 'PKPLocale::registerLocaleFile::isValidLocaleFile', 'PKPLocale::translate', 'API::submissions::files::params', 'ArticleGalleyDAO::getLocalizedGalleysByArticle', 'PluginGridHandler::plugin', 'PluginGridHandler::plugin', 'SubmissionFile::assignedFileStages', 'SubmissionHandler::saveSubmit'); // From the 3.4.0 Release Notebook; remove for 3.6.0 development branch
         Hook::addUnsupportedHooks('AcronPlugin::parseCronTab'); // pkp/pkp-lib#9678 Unavailable since stable-3_5_0;
         Hook::addUnsupportedHooks('Announcement::delete::before', 'Announcement::delete', 'Announcement::Collector'); // pkp/pkp-lib#10328 Unavailable since stable-3_5_0, use Eloquent Model events instead
-
+        Hook::addUnsupportedHooks('UserGroup::delete::before','UserGroup::delete'); // unavailable since stable-3_6_0, use Eloquent Model events instead
         // If not in strict mode, globally expose constants on this class.
         if (!PKP_STRICT_MODE) {
             foreach ([
diff --git a/classes/core/PKPPageRouter.php b/classes/core/PKPPageRouter.php
index 9f14fc29d1f..e9a0cbe2e05 100644
--- a/classes/core/PKPPageRouter.php
+++ b/classes/core/PKPPageRouter.php
@@ -25,6 +25,9 @@
 use PKP\plugins\Hook;
 use PKP\security\Role;
 use PKP\security\Validation;
+use PKP\userGroup\UserGroup;
+use PKP\userGroup\relationships\UserUserGroup;
+
 
 class PKPPageRouter extends PKPRouter
 {
@@ -402,50 +405,70 @@ public function getHomeUrl(PKPRequest $request): string
         $userId = $user->getId();
 
         if ($context = $this->getContext($request)) {
-            // If the user has no roles, or only one role and this is reader, go to "Index" page.
-            // Else go to "submissions" page
-            $userGroups = Repo::userGroup()->userUserGroups($userId, $context->getId());
-
+            // fetch user groups for the user in the current context
+            $userGroups = UserGroup::query()
+                ->where('context_id', $context->getId())
+                ->whereHas('userUserGroups', function ($query) use ($userId) {
+                    $query->where('user_id', $userId)
+                        ->where(function ($q) {
+                            $q->whereNull('date_end')
+                              ->orWhere('date_end', '>', now());
+                        })
+                        ->where(function ($q) {
+                            $q->whereNull('date_start')
+                              ->orWhere('date_start', '<=', now());
+                        });
+                })
+                ->get();
+    
             if ($userGroups->isEmpty()
-                || ($userGroups->count() == 1 && $userGroups->first()->getRoleId() == Role::ROLE_ID_READER)
+                || ($userGroups->count() == 1 && $userGroups->first()->role_id == Role::ROLE_ID_READER)
             ) {
                 return $request->url(null, 'index');
             }
 
             if(Config::getVar('features', 'enable_new_submission_listing')) {
 
-                $roleIds = $userGroups->map(function ($group) {
-                    return $group->getRoleId();
-                });
-
-                $roleIdsArray = $roleIds->all();
+                $roleIdsArray = $userGroups->pluck('role_id')->all();
 
-                if (count(array_intersect([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN, Role::ROLE_ID_SUB_EDITOR, Role::ROLE_ID_ASSISTANT], $roleIdsArray))) {
+                if (array_intersect([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN, Role::ROLE_ID_SUB_EDITOR, Role::ROLE_ID_ASSISTANT], $roleIdsArray)) {
                     return $request->url(null, 'dashboard', 'editorial');
 
                 }
-                if(count(array_intersect([ Role::ROLE_ID_REVIEWER], $roleIdsArray))) {
+                if (in_array(Role::ROLE_ID_REVIEWER, $roleIdsArray)) {
                     return $request->url(null, 'dashboard', 'reviewAssignments');
-
                 }
-                if(count(array_intersect([  Role::ROLE_ID_AUTHOR], $roleIdsArray))) {
+                if (in_array(Role::ROLE_ID_AUTHOR, $roleIdsArray)) {
                     return $request->url(null, 'dashboard', 'mySubmissions');
                 }
             }
 
             return $request->url(null, 'submissions');
         } else {
-            // The user is at the site context, check to see if they are
-            // only registered in one place w/ one role
-            $userGroups = Repo::userGroup()->userUserGroups($userId, \PKP\core\PKPApplication::SITE_CONTEXT_ID);
+            // The user is at the site context
+            $userGroups = UserGroup::query()
+                ->where('context_id', \PKP\core\PKPApplication::SITE_CONTEXT_ID)
+                ->whereHas('userUserGroups', function ($query) use ($userId) {
+                    $query->where('user_id', $userId)
+                        ->where(function ($q) {
+                            $q->whereNull('date_end')
+                              ->orWhere('date_end', '>', now());
+                        })
+                        ->where(function ($q) {
+                            $q->whereNull('date_start')
+                              ->orWhere('date_start', '<=', now());
+                        });
+                })
+                ->get();
+
             if ($userGroups->count() == 1) {
                 $firstUserGroup = $userGroups->first();
                 $contextDao = Application::getContextDAO();
-                $context = $contextDao->getById($firstUserGroup->getContextId());
+                $context = $contextDao->getById($firstUserGroup->context_id);
                 if (!isset($context)) {
                     $request->redirect(Application::SITE_CONTEXT_PATH, 'index');
                 }
-                if ($firstUserGroup->getRoleId() == Role::ROLE_ID_READER) {
+                if ($firstUserGroup->role_id == Role::ROLE_ID_READER) {
                     $request->redirect(null, 'index');
                 }
             }
diff --git a/classes/core/SettingsBuilder.php b/classes/core/SettingsBuilder.php
index b7b1a408375..f8de1fbeb22 100644
--- a/classes/core/SettingsBuilder.php
+++ b/classes/core/SettingsBuilder.php
@@ -24,6 +24,7 @@
 use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Str;
 use stdClass;
+use PKP\facades\Locale;
 
 class SettingsBuilder extends Builder
 {
@@ -161,36 +162,36 @@ public function where($column, $operator = null, $value = null, $boolean = 'and'
         if ($column instanceof ConditionExpression || $column instanceof Closure) {
             return parent::where($column, $operator, $value, $boolean);
         }
-
-        $settings = [];
-        $primaryColumn = false;
-
-        // See Illuminate\Database\Query\Builder::where()
+    
+        // Prepare value and operator
         [$value, $operator] = $this->query->prepareValueAndOperator(
             $value,
             $operator,
             func_num_args() === 2
         );
-
+    
         $modelSettingsList = $this->model->getSettings();
-
+    
+        $settings = [];
+        $primaryColumn = null;
+    
         if (is_string($column)) {
             if (in_array($column, $modelSettingsList)) {
                 $settings[$column] = $value;
             } else {
-                $primaryColumn = $column;
+                $primaryColumn = $this->getSnakeKey($column);
             }
+        } elseif (is_array($column)) {
+            $settings = array_intersect_key($column, array_flip($modelSettingsList));
+            $primaryColumn = array_diff_key($column, $settings);
+            $primaryColumn = array_map([$this, 'getSnakeKey'], array_keys($primaryColumn));
         }
-
-        if (is_array($column)) {
-            $settings = array_intersect($column, $modelSettingsList);
-            $primaryColumn = array_diff($column, $modelSettingsList);
-        }
-
+    
         if (empty($settings)) {
-            return parent::where($column, $operator, $value, $boolean);
+            return parent::where($primaryColumn ?? $column, $operator, $value, $boolean);
         }
-
+    
+        // Handle settings
         $where = [];
         foreach ($settings as $settingName => $settingValue) {
             $where = array_merge($where, [
@@ -198,19 +199,24 @@ public function where($column, $operator = null, $value = null, $boolean = 'and'
                 'setting_value' => $settingValue,
             ]);
         }
-
+    
         $this->query->whereIn(
             $this->model->getKeyName(),
             fn (QueryBuilder $query) =>
             $query->select($this->model->getKeyName())->from($this->model->getSettingsTable())->where($where, null, null, $boolean)
         );
-
+    
         if (!empty($primaryColumn)) {
             parent::where($primaryColumn, $operator, $value, $boolean);
         }
-
+    
         return $this;
     }
+    
+    protected function getSnakeKey($key)
+    {
+        return Str::snake($key);
+    }
 
     /**
      * Add a "where in" clause to the query.
@@ -224,10 +230,16 @@ public function where($column, $operator = null, $value = null, $boolean = 'and'
      */
     public function whereIn($column, $values, $boolean = 'and', $not = false)
     {
-        if ($column instanceof Expression || !in_array($column, $this->model->getSettings())) {
+        if ($column instanceof Expression) {
             return parent::whereIn($column, $values, $boolean, $not);
         }
-
+    
+        $column = $this->getSnakeKey($column);
+    
+        if (!in_array($column, $this->model->getSettings())) {
+            return parent::whereIn($column, $values, $boolean, $not);
+        }
+    
         $this->query->whereIn(
             $this->model->getKeyName(),
             fn (QueryBuilder $query) =>
@@ -237,9 +249,10 @@ public function whereIn($column, $values, $boolean = 'and', $not = false)
                 ->where('setting_name', $column)
                 ->whereIn('setting_value', $values, $boolean, $not)
         );
-
+    
         return $this;
     }
+    
 
     /*
      * Augment model with data from the settings table
diff --git a/classes/decision/DecisionType.php b/classes/decision/DecisionType.php
index 511714da168..df0cf9474ee 100644
--- a/classes/decision/DecisionType.php
+++ b/classes/decision/DecisionType.php
@@ -262,7 +262,7 @@ protected function getAssignedAuthorIds(Submission $submission): array
             ->withRoleIds([Role::ROLE_ID_AUTHOR])
             ->withStageIds([$this->getStageId()])
             ->get()
-            ->pluck('userId')
+            ->pluck('user_id')
             ->all();
     }
 
diff --git a/classes/decision/Repository.php b/classes/decision/Repository.php
index 79d1f81a6bd..553eb376938 100644
--- a/classes/decision/Repository.php
+++ b/classes/decision/Repository.php
@@ -428,7 +428,7 @@ protected function updateNotifications(Decision $decision, DecisionType $decisio
             ->withRoleIds([Role::ROLE_ID_AUTHOR])
             ->withStageIds([$decisionType->getStageId()])
             ->get()
-            ->pluck('userId')
+            ->pluck('user_id')
             ->all();
 
         $notificationMgr->updateNotification(
diff --git a/classes/decision/Steps.php b/classes/decision/Steps.php
index c8a31c509f0..2a97287a596 100644
--- a/classes/decision/Steps.php
+++ b/classes/decision/Steps.php
@@ -81,7 +81,7 @@ public function getStageParticipants(int $roleId): array
             ->withRoleIds([$roleId])
             ->withStageIds([$this->decisionType->getStageId()])
             ->get()
-            ->pluck('userId')
+            ->pluck('user_id')
             ->all();
 
         $users = [];
@@ -119,7 +119,7 @@ public function getDecidingEditors(): array
             ->withRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR])
             ->withRecommendOnly(false)
             ->get()
-            ->pluck('userId')
+            ->pluck('user_id')
             ->all();
 
         $users = [];
diff --git a/classes/install/PKPInstall.php b/classes/install/PKPInstall.php
index eb39b49e6c0..72f88cc21ba 100644
--- a/classes/install/PKPInstall.php
+++ b/classes/install/PKPInstall.php
@@ -43,6 +43,7 @@
 use PKP\services\PKPSchemaService;
 use PKP\site\SiteDAO;
 use PKP\site\Version;
+use PKP\userGroup\UserGroup;
 
 class PKPInstall extends Installer
 {
@@ -232,21 +233,31 @@ public function createData()
         Repo::user()->add($user);
 
         // Create an admin user group
-        $adminUserGroup = Repo::userGroup()->newDataObject();
-        $adminUserGroup->setRoleId(Role::ROLE_ID_SITE_ADMIN);
-        $adminUserGroup->setContextId(\PKP\core\PKPApplication::SITE_CONTEXT_ID);
-        $adminUserGroup->setDefault(true);
+        $adminUserGroup = new UserGroup([
+            'roleId' => Role::ROLE_ID_SITE_ADMIN,
+            'contextId' => \PKP\core\PKPApplication::SITE_CONTEXT_ID,
+            'isDefault' => true,
+        ]);
+
+        // Prepare multilingual 'name' and 'namePlural' settings
+        $names = [];
+        $namePlurals = [];
         foreach ($this->installedLocales as $locale) {
-            $name = __('default.groups.name.siteAdmin', [], $locale);
-            $namePlural = __('default.groups.plural.siteAdmin', [], $locale);
-            $adminUserGroup->setData('name', $name, $locale);
-            $adminUserGroup->setData('namePlural', $namePlural, $locale);
+            $names[$locale] = __('default.groups.name.siteAdmin', [], $locale);
+            $namePlurals[$locale] = __('default.groups.plural.siteAdmin', [], $locale);
         }
-        Repo::userGroup()->add($adminUserGroup);
 
-        // Put the installer into this user group
-        Repo::userGroup()->assignUserToGroup($user->getId(), $adminUserGroup->getId());
+        // Set the 'name' and 'namePlural' settings
+        $adminUserGroup->setData('name', $names);
+        $adminUserGroup->setData('namePlural', $namePlurals);
+
+        // Save the UserGroup to the database
+        $adminUserGroup->save();
 
+        // Assign the user to the admin user group
+        $repository = Repo::userGroup();
+        $repository->assignUserToGroup($user->getId(), $adminUserGroup->userGroupId);
+        
         // Add initial site data
         /** @var SiteDAO */
         $siteDao = DAORegistry::getDAO('SiteDAO');
diff --git a/classes/invitation/invitations/userRoleAssignment/helpers/UserGroupHelper.php b/classes/invitation/invitations/userRoleAssignment/helpers/UserGroupHelper.php
index 9908053974d..0e05778a1ad 100644
--- a/classes/invitation/invitations/userRoleAssignment/helpers/UserGroupHelper.php
+++ b/classes/invitation/invitations/userRoleAssignment/helpers/UserGroupHelper.php
@@ -32,7 +32,7 @@ public function __construct(
 
     public function getUserGroup()
     {
-        $this->userGroup = Repo::userGroup()->get($this->userGroupId);
+        $this->userGroup = UserGroup::find($this->userGroupId);
     }
 
     public static function fromArray(array $data): self
diff --git a/classes/invitation/invitations/userRoleAssignment/resources/UserRoleAssignmentInviteResource.php b/classes/invitation/invitations/userRoleAssignment/resources/UserRoleAssignmentInviteResource.php
index a6eb4f6a073..9f54445f053 100644
--- a/classes/invitation/invitations/userRoleAssignment/resources/UserRoleAssignmentInviteResource.php
+++ b/classes/invitation/invitations/userRoleAssignment/resources/UserRoleAssignmentInviteResource.php
@@ -18,6 +18,7 @@
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\JsonResource;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 class UserRoleAssignmentInviteResource extends JsonResource
 {
@@ -70,11 +71,11 @@ public function toArray(Request $request)
     protected function transformUserGroups(?array $userGroups)
     {
         return collect($userGroups)->map(function ($userGroup) {
-            $userGroupModel = Repo::userGroup()->get($userGroup['userGroupId']);
+            $userGroupModel = UserGroup::find($userGroup['userGroupId']);
 
             return [
                 'userGroupId' => $userGroup['userGroupId'],
-                'userGroupName' => $userGroupModel->getName(null),
+                'userGroupName' => $userGroupModel ? $userGroupModel->getLocalizedData('name') : null,
                 'masthead' => $userGroup['masthead'],
                 'dateStart' => $userGroup['dateStart'],
                 'dateEnd' => $userGroup['dateEnd'],
diff --git a/classes/invitation/invitations/userRoleAssignment/rules/UserGroupExistsRule.php b/classes/invitation/invitations/userRoleAssignment/rules/UserGroupExistsRule.php
index 775e1d08445..e7c4db8c939 100644
--- a/classes/invitation/invitations/userRoleAssignment/rules/UserGroupExistsRule.php
+++ b/classes/invitation/invitations/userRoleAssignment/rules/UserGroupExistsRule.php
@@ -14,8 +14,8 @@
 
 namespace PKP\invitation\invitations\userRoleAssignment\rules;
 
-use APP\facades\Repo;
 use Illuminate\Contracts\Validation\Rule;
+use PKP\userGroup\UserGroup;
 
 class UserGroupExistsRule implements Rule
 {
@@ -23,10 +23,9 @@ class UserGroupExistsRule implements Rule
     public function passes($attribute, $value)
     {
         $this->userGroupId = $value;
-        $userGroup = Repo::userGroup()->get($value);
+        $userGroup = UserGroup::find($value);
         return isset($userGroup);
     }
-
     public function message()
     {
         return __('invitation.userRoleAssignment.validation.error.addUserRoles.userGroupNotExisting', [
diff --git a/classes/mail/mailables/UserRoleAssignmentInvitationNotify.php b/classes/mail/mailables/UserRoleAssignmentInvitationNotify.php
index bf45a7c6bb6..21456f48312 100644
--- a/classes/mail/mailables/UserRoleAssignmentInvitationNotify.php
+++ b/classes/mail/mailables/UserRoleAssignmentInvitationNotify.php
@@ -27,7 +27,7 @@
 use PKP\mail\traits\Sender;
 use PKP\security\Role;
 use PKP\userGroup\relationships\UserUserGroup;
-use UserGroup;
+use PKP\userGroup\UserGroup;
 
 class UserRoleAssignmentInvitationNotify extends Mailable
 {
@@ -94,20 +94,15 @@ private function getAllUserUserGroupSection(array $userUserGroups, ?UserGroup $u
 
         $count = 1;
         foreach ($userUserGroups as $userUserGroup) {
-            if ($userUserGroup instanceof UserUserGroup) {
-                $userGroupHelper = UserGroupHelper::fromUserUserGroup($userUserGroup);
-            } else {
-                $userGroupHelper = UserGroupHelper::fromArray($userUserGroup);
-            }
-            
+            $userGroupHelper = $userUserGroup instanceof UserUserGroup
+                ? UserGroupHelper::fromUserUserGroup($userUserGroup)
+                : UserGroupHelper::fromArray($userUserGroup);
+    
             if ($count == 1) {
                 $retString = $title;
             }
 
-            $userGroupToUse = $userGroup;
-            if (!isset($userGroupToUse)) {
-                $userGroupToUse = Repo::userGroup()->get($userGroupHelper->userGroupId);
-            }
+            $userGroupToUse = $userGroup ?? UserGroup::find($userGroupHelper->userGroupId);
 
             $userGroupSection = $this->getUserUserGroupSection($userGroupHelper, $userGroupToUse, $context, $count, $locale);
 
@@ -132,7 +127,7 @@ private function getUserUserGroupSection(UserGroupHelper $userUserGroup, UserGro
         $sectionMastheadAppear = __('emails.userRoleAssignmentInvitationNotify.userGroupSectionWillNotAppear', 
             [
                 'contextName' => $context->getName($locale),
-                'sectionName' => $userGroup->getName($locale)
+                'sectionName' => $userGroup->getLocalizedData('name', $locale)
             ]
         );
 
@@ -140,7 +135,7 @@ private function getUserUserGroupSection(UserGroupHelper $userUserGroup, UserGro
             $sectionMastheadAppear = __('emails.userRoleAssignmentInvitationNotify.userGroupSectionWillAppear', 
                 [
                     'contextName' => $context->getName($locale),
-                    'sectionName' => $userGroup->getName($locale)
+                    'sectionName' => $userGroup->getLocalizedData('name', $locale)
                 ]
             );
         }
@@ -148,7 +143,7 @@ private function getUserUserGroupSection(UserGroupHelper $userUserGroup, UserGro
         $userGroupSection = __('emails.userRoleAssignmentInvitationNotify.userGroupSection', 
             [
                 'sectionNumber' => $count, 
-                'sectionName' => $userGroup->getName($locale),
+                'sectionName' => $userGroup->getLocalizedData('name', $locale),
                 'dateStart' => $userUserGroup->dateStart,
                 'sectionEndingDate' => $sectionEndingDate,
                 'sectionMastheadAppear' => $sectionMastheadAppear
@@ -192,24 +187,35 @@ public function setData(?string $locale = null): void
             foreach ($this->invitation->getPayload()->userGroupsToRemove as $userUserGroup) {
                 $userGroupHelper = UserGroupHelper::fromArray($userUserGroup);
                 
-                $userGroup = Repo::userGroup()->get($userGroupHelper->userGroupId);
+                // Replace the repository call with UserGroup::find()
+                $userGroup = UserGroup::find($userGroupHelper->userGroupId);
+                
+                // Fetch the user-user group relationships
                 $userUserGroups = UserUserGroup::withUserId($user->getId())
-                    ->withUserGroupId($userGroup->getId())
+                    ->withUserGroupId($userGroup->id)
                     ->withActive()
                     ->get();
                 
-                $userGroupsRemoved = $this->getAllUserUserGroupSection($userUserGroups->toArray(), $userGroup, $context, $locale, $userGroupsRemovedTitle);
+                // Process the user groups removed
+                $userGroupsRemoved = $this->getAllUserUserGroupSection(
+                    $userUserGroups->toArray(),
+                    $userGroup,
+                    $context,
+                    $locale,
+                    $userGroupsRemovedTitle
+                );
             }
 
             // Existing Roles
-            $userGroups = Repo::userGroup()->getCollector()
-                ->filterByContextIds([$this->invitation->getContextId()])
-                ->filterByUserIds([$user->getId()])
-                ->getMany();
+
+            $userGroups = UserGroup::query()
+                ->withContextIds([$this->invitation->getContextId()])
+                ->withUserIds([$user->getId()])
+                ->get();
             
             foreach ($userGroups as $userGroup) {
                 $userUserGroups = UserUserGroup::withUserId($user->getId())
-                    ->withUserGroupId($userGroup->getId())
+                    ->withUserGroupId($userGroup->id)
                     ->withActive()
                     ->get();
                 
diff --git a/classes/notification/managerDelegate/PendingRevisionsNotificationManager.php b/classes/notification/managerDelegate/PendingRevisionsNotificationManager.php
index dbf3c219052..463ec6d42bd 100644
--- a/classes/notification/managerDelegate/PendingRevisionsNotificationManager.php
+++ b/classes/notification/managerDelegate/PendingRevisionsNotificationManager.php
@@ -95,7 +95,18 @@ public function getNotificationTitle(Notification $notification): string
      */
     public function updateNotification(PKPRequest $request, ?array $userIds, int $assocType, int $assocId): void
     {
+        if (empty($userIds)) {
+            // no user IDs provided; nothing to update
+            return;
+        }
+    
         $userId = current($userIds);
+    
+        if (!$userId || !is_int($userId) || $userId <= 0) {
+            // invalid user ID; skip notification creation
+            return;
+        }
+    
         $submissionId = $assocId;
         $stageData = $this->_getStageDataByType();
         if ($stageData == null) {
diff --git a/classes/observers/listeners/RestrictAuthorAssignment.php b/classes/observers/listeners/RestrictAuthorAssignment.php
index a3c58ce22bb..079900be931 100644
--- a/classes/observers/listeners/RestrictAuthorAssignment.php
+++ b/classes/observers/listeners/RestrictAuthorAssignment.php
@@ -21,6 +21,7 @@
 use PKP\observers\events\SubmissionSubmitted;
 use PKP\security\Role;
 use PKP\stageAssignment\StageAssignment;
+use PKP\userGroup\UserGroup;
 
 class RestrictAuthorAssignment
 {
@@ -40,12 +41,12 @@ public function handle(SubmissionSubmitted $event)
             ->get();
 
         foreach ($stageAssignments as $stageAssignment) {
-            $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId, $event->context->getId());
+            $userGroup = UserGroup::findById($stageAssignment->userGroupId, $event->context->getId());
             if (!$userGroup) {
                 continue;
             }
             
-            $stageAssignment->canChangeMetadata = $userGroup->getPermitMetadataEdit();
+            $stageAssignment->canChangeMetadata = $userGroup->permitMetadataEdit;
             $stageAssignment->save();
         }
     }
diff --git a/classes/observers/listeners/SendSubmissionAcknowledgement.php b/classes/observers/listeners/SendSubmissionAcknowledgement.php
index cdc1392f2ae..4e18043c474 100644
--- a/classes/observers/listeners/SendSubmissionAcknowledgement.php
+++ b/classes/observers/listeners/SendSubmissionAcknowledgement.php
@@ -47,7 +47,7 @@ public function handle(SubmissionSubmitted $event)
         $assignedUserIds = StageAssignment::withSubmissionIds([$event->submission->getId()])
             ->withRoleIds([Role::ROLE_ID_AUTHOR])
             ->get()
-            ->pluck('userId')
+            ->pluck('user_id')
             ->all();
 
         $submitterUsers = Repo::user()
diff --git a/classes/observers/listeners/UpdateAuthorStageAssignments.php b/classes/observers/listeners/UpdateAuthorStageAssignments.php
index 039c9bd7e9e..ffaf243b27d 100644
--- a/classes/observers/listeners/UpdateAuthorStageAssignments.php
+++ b/classes/observers/listeners/UpdateAuthorStageAssignments.php
@@ -22,6 +22,7 @@
 use PKP\observers\events\SubmissionSubmitted;
 use PKP\security\Role;
 use PKP\stageAssignment\StageAssignment;
+use PKP\userGroup\UserGroup;
 
 class UpdateAuthorStageAssignments
 {
@@ -41,18 +42,16 @@ public function handle(SubmissionSubmitted $event)
             ->withStageIds([$event->submission->getData('stageId')])
             ->get();
 
-        $userGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$event->context->getId()])
-            ->filterByRoleIds([Role::ROLE_ID_AUTHOR])
-            ->getMany();
+            $userGroups = UserGroup::withContextIds([$event->context->getId()])
+            ->withRoleIds([Role::ROLE_ID_AUTHOR])
+            ->get();
 
         foreach ($stageAssigments as $stageAssignment) {
             $userGroup = $userGroups->get($stageAssignment->userGroupId);
-            if (!$userGroup || $stageAssignment->canChangeMetadata === $userGroup->getPermitMetadataEdit()) {
+            if (!$userGroup || $stageAssignment->canChangeMetadata === $userGroup->permitMetadataEdit) {
                 continue;
             }
-            $stageAssignment->canChangeMetadata = $userGroup->getPermitMetadataEdit();
+            $stageAssignment->canChangeMetadata = $userGroup->permitMetadataEdit;
             $stageAssignment->save();
         }
     }
diff --git a/classes/orcid/PKPOrcidWork.php b/classes/orcid/PKPOrcidWork.php
index 407ddf81bbb..e80bfb61bf3 100644
--- a/classes/orcid/PKPOrcidWork.php
+++ b/classes/orcid/PKPOrcidWork.php
@@ -258,7 +258,8 @@ private function buildOrcidContributors(array $authors, Context $context, Public
             ];
 
             $userGroup = $author->getUserGroup();
-            $role = self::USER_GROUP_TO_ORCID_ROLE[$userGroup->getName('en')];
+            $roleName = $userGroup->getLocalizedData('name', 'en');
+            $role = self::USER_GROUP_TO_ORCID_ROLE[$roleName];
 
             if ($role) {
                 $contributor['contributor-attributes']['contributor-role'] = $role;
diff --git a/classes/publication/PKPPublication.php b/classes/publication/PKPPublication.php
index 849eb63b9fe..f726e88775f 100644
--- a/classes/publication/PKPPublication.php
+++ b/classes/publication/PKPPublication.php
@@ -190,23 +190,24 @@ public function getAuthorString(\Traversable $userGroups, $includeInBrowseOnly =
         }
 
         if ($includeInBrowseOnly) {
-            $authors = $authors->filter(function ($author, $key) {
-                return $author->getData('includeInBrowse');
-            });
+            $authors = $authors->filter(fn($author) => $author->getData('includeInBrowse'));
+        }
+
+        // create a mapping of user group ids to user groups for quick lookup
+        $userGroupMap = [];
+        foreach ($userGroups as $userGroup) {
+            $userGroupMap[$userGroup->id] = $userGroup;
         }
 
         $str = '';
         $lastUserGroupId = null;
         foreach ($authors as $author) {
+            $currentUserGroupId = $author->getUserGroupId();
             if (!empty($str)) {
-                if ($lastUserGroupId != $author->getData('userGroupId')) {
-                    foreach ($userGroups as $userGroup) {
-                        if ($lastUserGroupId === $userGroup->getId()) {
-                            if ($userGroup->getData('showTitle')) {
-                                $str .= ' (' . $userGroup->getLocalizedData('name') . ')';
-                            }
-                            break;
-                        }
+                if ($lastUserGroupId !== $currentUserGroupId) {
+                    $lastUserGroup = $userGroupMap[$lastUserGroupId] ?? null;
+                    if ($lastUserGroup && $lastUserGroup->showTitle) {
+                        $str .= ' (' . $lastUserGroup->getLocalizedData('name') . ')';
                     }
                     $str .= __('common.semicolonListSeparator');
                 } else {
@@ -214,18 +215,14 @@ public function getAuthorString(\Traversable $userGroups, $includeInBrowseOnly =
                 }
             }
             $str .= $author->getFullName();
-            $lastUserGroupId = $author->getUserGroupId();
+            $lastUserGroupId = $currentUserGroupId;
         }
 
         // If there needs to be a trailing user group title, add it
         if (isset($author)) {
-            foreach ($userGroups as $userGroup) {
-                if ($author->getData('userGroupId') === $userGroup->getId()) {
-                    if ($userGroup->getData('showTitle')) {
-                        $str .= ' (' . $userGroup->getLocalizedData('name') . ')';
-                    }
-                    break;
-                }
+            $lastUserGroup = $userGroupMap[$author->getUserGroupId()] ?? null;
+            if ($lastUserGroup && $lastUserGroup->showTitle) {
+                $str .= ' (' . $lastUserGroup->getLocalizedData('name') . ')';
             }
         }
 
diff --git a/classes/security/RoleDAO.php b/classes/security/RoleDAO.php
index 48cd849bfc1..9dbc7b29ebf 100644
--- a/classes/security/RoleDAO.php
+++ b/classes/security/RoleDAO.php
@@ -25,6 +25,7 @@
 use PKP\core\Core;
 use PKP\db\DAO;
 use PKP\db\DAORegistry;
+use PKP\userGroup\UserGroup;
 
 class RoleDAO extends DAO
 {
@@ -89,14 +90,26 @@ public function getByUserId(int $userId, ?int $contextId = Application::SITE_CON
      */
     public function getByUserIdGroupedByContext(int $userId)
     {
-        $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
-        $userGroups = Repo::userGroup()->userUserGroups($userId);
-
+        $userGroups = UserGroup::query()
+            ->with('userUserGroups')
+            ->whereHas('userUserGroups', function ($query) use ($userId) {
+                $query->where('user_id', $userId)
+                    ->where(function ($q) {
+                        $q->whereNull('date_end')
+                          ->orWhere('date_end', '>', now());
+                    })
+                    ->where(function ($q) {
+                        $q->whereNull('date_start')
+                          ->orWhere('date_start', '<=', now());
+                    });
+            })
+            ->get();
+    
         $roles = [];
         foreach ($userGroups as $userGroup) {
-            $role = $roleDao->newDataObject();
-            $role->setRoleId($userGroup->getRoleId());
-            $roles[(int) $userGroup->getContextId()][$userGroup->getRoleId()] = $role;
+            $role = $this->newDataObject();
+            $role->setRoleId($userGroup->role_id);
+            $roles[(int) $userGroup->context_id][$userGroup->role_id] = $role;
         }
 
         return $roles;
diff --git a/classes/security/Validation.php b/classes/security/Validation.php
index ffa499c611f..1831d88e820 100644
--- a/classes/security/Validation.php
+++ b/classes/security/Validation.php
@@ -26,6 +26,8 @@
 use PKP\site\Site;
 use PKP\site\SiteDAO;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
+use PKP\security\Role;
 
 class Validation
 {
@@ -396,42 +398,76 @@ public static function isSiteAdmin()
      */
     public static function canAdminister($administeredUserId, $administratorUserId)
     {
-        $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
-
         // You can administer yourself
         if ($administeredUserId == $administratorUserId) {
             return true;
         }
 
-        // You cannot administer administrators
-        if ($roleDao->userHasRole(\PKP\core\PKPApplication::SITE_CONTEXT_ID, $administeredUserId, Role::ROLE_ID_SITE_ADMIN)) {
+        $siteContextId = \PKP\core\PKPApplication::SITE_CONTEXT_ID;
+
+        // check if administered user is site admin
+        $isAdministeredUserSiteAdmin = UserGroup::query()
+            ->withContextIds($siteContextId)
+            ->withRoleIds(Role::ROLE_ID_SITE_ADMIN)
+            ->whereHas('userUserGroups', function ($query) use ($administeredUserId) {
+                $query->withUserId($administeredUserId)
+                      ->withActive();
+            })
+            ->exists();
+    
+        if ($isAdministeredUserSiteAdmin) {
             return false;
         }
-
-        // Otherwise, administrators can administer everyone
-        if ($roleDao->userHasRole(\PKP\core\PKPApplication::SITE_CONTEXT_ID, $administratorUserId, Role::ROLE_ID_SITE_ADMIN)) {
+    
+        // check if administrator user is site admin
+        $isAdministratorUserSiteAdmin = UserGroup::query()
+            ->withContextIds($siteContextId)
+            ->withRoleIds(Role::ROLE_ID_SITE_ADMIN)
+            ->whereHas('userUserGroups', function ($query) use ($administratorUserId) {
+                $query->withUserId($administratorUserId)
+                      ->withActive();
+            })
+            ->exists();
+    
+        if ($isAdministratorUserSiteAdmin) {
             return true;
         }
-
-        // Check for administered user group assignments in other contexts
-        // that the administrator user doesn't have a manager role in.
-        $userGroups = Repo::userGroup()->userUserGroups($administeredUserId);
-        foreach ($userGroups as $userGroup) {
-            if ($userGroup->getContextId() != \PKP\core\PKPApplication::SITE_CONTEXT_ID && !$roleDao->userHasRole($userGroup->getContextId(), $administratorUserId, Role::ROLE_ID_MANAGER)) {
-                // Found an assignment: disqualified.
-                return false;
-            }
+    
+        // Get contexts where administered user has roles
+        $administeredUserContexts = UserGroup::query()
+            ->whereHas('userUserGroups', function ($query) use ($administeredUserId) {
+                $query->withUserId($administeredUserId)
+                      ->withActive();
+            })
+            ->get()
+            ->map(fn ($userGroup) => $userGroup->contextId)
+            ->unique()
+            ->values()
+            ->toArray();
+    
+        // get contexts where administrator user has manager role
+        $administratorManagerContexts = UserGroup::query()
+            ->withRoleIds(Role::ROLE_ID_MANAGER)
+            ->whereHas('userUserGroups', function ($query) use ($administratorUserId) {
+                $query->withUserId($administratorUserId)
+                      ->withActive();
+            })
+            ->get()
+            ->map(fn ($userGroup) => $userGroup->contextId)
+            ->unique()
+            ->values()
+            ->toArray();
+    
+        // check for conflicting contexts
+        $conflictingContexts = array_diff($administeredUserContexts, $administratorManagerContexts);
+    
+        if (!empty($conflictingContexts)) {
+            // found conflicting contexts: disqualified
+            return false;
         }
 
         // Make sure the administering user has a manager role somewhere
-        $foundManagerRole = false;
-        $roles = $roleDao->getByUserId($administratorUserId);
-        foreach ($roles as $role) {
-            if ($role->getRoleId() == Role::ROLE_ID_MANAGER) {
-                $foundManagerRole = true;
-            }
-        }
-        if (!$foundManagerRole) {
+        if (empty($administratorManagerContexts)) {
             return false;
         }
 
@@ -454,63 +490,73 @@ public static function getAdministrationLevel(int $administeredUserId, int $admi
         if ($administeredUserId == $administratorUserId) {
             return self::ADMINISTRATION_FULL;
         }
-
-        $filteredSiteAdminUserGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([\PKP\core\PKPApplication::SITE_CONTEXT_ID])
-            ->filterByRoleIds([Role::ROLE_ID_SITE_ADMIN]);
-
-        // You cannot administer administrators
-        if ($filteredSiteAdminUserGroups->filterByUserIds([$administeredUserId])->getCount() > 0) {
+    
+        $siteContextId = \PKP\core\PKPApplication::SITE_CONTEXT_ID;
+    
+        // Check if administered user is site admin
+        $isAdministeredUserSiteAdmin = UserGroup::query()
+            ->withContextIds($siteContextId)
+            ->withRoleIds(Role::ROLE_ID_SITE_ADMIN)
+            ->whereHas('userUserGroups', function ($query) use ($administeredUserId) {
+                $query->withUserId($administeredUserId)
+                      ->withActive();
+            })
+            ->exists();
+    
+        if ($isAdministeredUserSiteAdmin) {
             return self::ADMINISTRATION_PROHIBITED;
         }
-
-        // Otherwise, administrators can administer everyone
-        if ($filteredSiteAdminUserGroups->filterByUserIds([$administratorUserId])->getCount() > 0) {
+    
+        // Check if administrator user is site admin
+        $isAdministratorUserSiteAdmin = UserGroup::query()
+            ->withContextIds($siteContextId)
+            ->withRoleIds(Role::ROLE_ID_SITE_ADMIN)
+            ->whereHas('userUserGroups', function ($query) use ($administratorUserId) {
+                $query->withUserId($administratorUserId)
+                      ->withActive();
+            })
+            ->exists();
+    
+        if ($isAdministratorUserSiteAdmin) {
             return self::ADMINISTRATION_FULL;
         }
 
-        // Make sure the administering user has a manager role somewhere
-        $roleManagerCount = Repo::userGroup()
-            ->getCollector()
-            ->filterByUserIds([$administratorUserId])
-            ->filterByRoleIds([Role::ROLE_ID_MANAGER])
-            ->getCount();
-
-        if ($roleManagerCount <= 0) {
+        // Get contexts where administrator has manager role
+        $administratorManagerContexts = UserGroup::query()
+            ->withRoleIds(Role::ROLE_ID_MANAGER)
+            ->whereHas('userUserGroups', function ($query) use ($administratorUserId) {
+                $query->withUserId($administratorUserId)
+                      ->withActive();
+            })
+            ->get()
+            ->map(fn ($userGroup) => $userGroup->contextId)
+            ->unique()
+            ->values()
+            ->toArray();
+    
+        // Ensure the administrator has a manager role somewhere
+        if (empty($administratorManagerContexts)) {
             return self::ADMINISTRATION_PROHIBITED;
         }
-
-        $administeredUserAssignedGroupIds = Repo::userGroup()
-            ->getCollector()
-            ->filterByUserIds([$administeredUserId])
-            ->getMany()
-            ->map(fn ($userGroup) => $userGroup->getContextId())
-            ->sort()
+    
+        // Get contexts where administered user has roles
+        $administeredUserContexts = UserGroup::query()
+            ->whereHas('userUserGroups', function ($query) use ($administeredUserId) {
+                $query->withUserId($administeredUserId)
+                      ->withActive();
+            })
+            ->get()
+            ->map(fn ($userGroup) => $userGroup->contextId)
+            ->unique()
+            ->values()
             ->toArray();
-
-        $administratorUserAssignedGroupIds = Repo::userGroup()
-            ->getCollector()
-            ->filterByUserIds([$administratorUserId])
-            ->filterByRoleIds([Role::ROLE_ID_MANAGER])
-            ->getMany()
-            ->map(fn ($userGroup) => $userGroup->getContextId())
-            ->sort()
-            ->toArray();
-
-        // Check for administered user group assignments in other contexts
-        // that the administrator user doesn't have a manager role in.
-        if (collect($administeredUserAssignedGroupIds)->diff($administratorUserAssignedGroupIds)->count() > 0) {
-            // Found an assignment: disqualified.
-            // But also determine if a partial administrate is allowed
-            // if the Administrator User is a Journal Manager in the current context
-            if ($contextId !== null &&
-                Repo::userGroup()
-                    ->getCollector()
-                    ->filterByContextIds([$contextId])
-                    ->filterByUserIds([$administratorUserId])
-                    ->filterByRoleIds([Role::ROLE_ID_MANAGER])
-                    ->getCount()) {
+    
+        // Check for conflicting contexts
+        $conflictingContexts = array_diff($administeredUserContexts, $administratorManagerContexts);
+    
+        if (!empty($conflictingContexts)) {
+            // Check for partial administration
+            if ($contextId !== null && in_array($contextId, $administratorManagerContexts)) {
                 return self::ADMINISTRATION_PARTIAL;
             }
             return self::ADMINISTRATION_PROHIBITED;
diff --git a/classes/security/authorization/StageRolePolicy.php b/classes/security/authorization/StageRolePolicy.php
index 99929128a1c..69dbd2cdb93 100644
--- a/classes/security/authorization/StageRolePolicy.php
+++ b/classes/security/authorization/StageRolePolicy.php
@@ -21,6 +21,7 @@
 use APP\facades\Repo;
 use PKP\security\Role;
 use PKP\stageAssignment\StageAssignment;
+use PKP\userGroup\UserGroup;
 
 class StageRolePolicy extends AuthorizationPolicy
 {
@@ -79,8 +80,8 @@ public function effect()
                 ->get();
 
             foreach ($stageAssignments as $stageAssignment) {
-                $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
-                if (in_array($userGroup->getRoleId(), $this->_roleIds) && !$stageAssignment->recommendOnly) {
+                $userGroup = UserGroup::findById($stageAssignment->userGroupId);
+                if ($userGroup && in_array($userGroup->roleId, $this->_roleIds) && !$stageAssignment->recommendOnly) {
                     return AuthorizationPolicy::AUTHORIZATION_PERMIT;
                 }
             }
@@ -101,8 +102,8 @@ public function effect()
             $noResults = true;
             foreach ($stageAssignments as $stageAssignment) {
                 $noResults = false;
-                $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
-                if ($userGroup->getRoleId() == Role::ROLE_ID_MANAGER && !$stageAssignment->recommendOnly) {
+                $userGroup = UserGroup::find($stageAssignment->userGroupId);
+                if ($userGroup && $userGroup->roleId == Role::ROLE_ID_MANAGER && !$stageAssignment->recommendOnly) {
                     return AuthorizationPolicy::AUTHORIZATION_PERMIT;
                 }
             }
diff --git a/classes/security/authorization/internal/DecisionAllowedPolicy.php b/classes/security/authorization/internal/DecisionAllowedPolicy.php
index 59f90ffe0fa..87651e89263 100644
--- a/classes/security/authorization/internal/DecisionAllowedPolicy.php
+++ b/classes/security/authorization/internal/DecisionAllowedPolicy.php
@@ -22,6 +22,7 @@
 use PKP\security\Role;
 use PKP\stageAssignment\StageAssignment;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 class DecisionAllowedPolicy extends AuthorizationPolicy
 {
@@ -67,8 +68,8 @@ public function effect()
         } else {
             $isAllowed = false;
             foreach ($stageAssignments as $stageAssignment) {
-                $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
-                if (!in_array($userGroup->getRoleId(), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR])) {
+                $userGroup = UserGroup::findById($stageAssignment->userGroupId);
+                if ($userGroup && !in_array($userGroup->roleId, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR])) {
                     continue;
                 }
                 if (Repo::decision()->isRecommendation($decisionType->getDecision()) && $stageAssignment->recommendOnly) {
diff --git a/classes/services/PKPContextService.php b/classes/services/PKPContextService.php
index fc8ab3fb4bf..cf65fe33eee 100644
--- a/classes/services/PKPContextService.php
+++ b/classes/services/PKPContextService.php
@@ -48,7 +48,11 @@
 use PKP\services\interfaces\EntityReadInterface;
 use PKP\services\interfaces\EntityWriteInterface;
 use PKP\submission\GenreDAO;
+use PKP\userGroup\Repository as UserGroupRepository;
 use PKP\validation\ValidatorFactory;
+use PKP\userGroup\UserGroup;
+use PKP\userGroup\relationships\UserUserGroup;
+
 
 abstract class PKPContextService implements EntityPropertyInterface, EntityReadInterface, EntityWriteInterface
 {
@@ -547,10 +551,29 @@ public function add($context, $request)
         $genreDao = DAORegistry::getDAO('GenreDAO'); /** @var GenreDAO $genreDao */
         $genreDao->installDefaults($context->getId(), $context->getData('supportedLocales'));
 
-        Repo::userGroup()->installSettings($context->getId(), 'registry/userGroups.xml');
-
-        $managerUserGroup = Repo::userGroup()->getByRoleIds([Role::ROLE_ID_MANAGER], $context->getId(), true)->firstOrFail();
-        Repo::userGroup()->assignUserToGroup($currentUser->getId(), $managerUserGroup->getId());
+        $userGroupRepository = app(UserGroupRepository::class);
+        $userGroupRepository->installSettings($context->getId(), 'registry/userGroups.xml');
+
+
+        $managerUserGroup = UserGroup::withContextIds([$context->getId()])
+            ->withRoleIds([Role::ROLE_ID_MANAGER])
+            ->isDefault(true)
+            ->firstOrFail();
+    
+        $assignmentExists = UserUserGroup::query()
+            ->withUserId($currentUser->getId())
+            ->withUserGroupId($managerUserGroup->id)
+            ->exists();
+    
+        if (!$assignmentExists) {
+            UserUserGroup::create([
+                'userId' => $currentUser->getId(),
+                'userGroupId' => $managerUserGroup->userGroupId,
+                'dateStart' => null,
+                'dateEnd' => null,
+                'masthead' => null,
+            ]);
+        }
 
         $fileManager = new FileManager();
         foreach ($this->installFileDirs as $dir) {
@@ -623,7 +646,7 @@ public function delete($context)
 
         Repo::reviewAssignment()->deleteByContextId($context->getId());
 
-        Repo::userGroup()->deleteByContextId($context->getId());
+        UserGroup::withContextIds($context->getId())->delete();
 
         $genreDao = DAORegistry::getDAO('GenreDAO'); /** @var GenreDAO $genreDao */
         $genreDao->deleteByContextId($context->getId());
diff --git a/classes/services/PKPSchemaService.php b/classes/services/PKPSchemaService.php
index b276636861e..7e1a8cbe41c 100644
--- a/classes/services/PKPSchemaService.php
+++ b/classes/services/PKPSchemaService.php
@@ -269,12 +269,12 @@ public function groupPropsByOrigin(string $schemaName, bool $excludeReadOnly = f
             if (empty($propSchema->origin)) {
                 continue;
             }
-
+    
             // Exclude readonly if specified
-            if ($excludeReadOnly && $propSchema->origin->readOnly) {
+            if ($excludeReadOnly && !empty($propSchema->readOnly)) {
                 continue;
             }
-
+    
             switch($propSchema->origin) {
                 case Schema::ATTRIBUTE_ORIGIN_SETTINGS:
                     $propsByOrigin[Schema::ATTRIBUTE_ORIGIN_SETTINGS][] = $propName;
@@ -288,9 +288,10 @@ public function groupPropsByOrigin(string $schemaName, bool $excludeReadOnly = f
                     break;
             }
         }
-
+    
         return $propsByOrigin;
     }
+    
 
     /**
      * Sanitize properties according to a schema
diff --git a/classes/stageAssignment/Repository.php b/classes/stageAssignment/Repository.php
index 01ecd814bbb..23e0d0797ea 100644
--- a/classes/stageAssignment/Repository.php
+++ b/classes/stageAssignment/Repository.php
@@ -20,6 +20,7 @@
 
 use APP\facades\Repo;
 use PKP\core\Core;
+use PKP\userGroup\UserGroup;
 
 class Repository
 {
@@ -29,7 +30,7 @@ class Repository
     public function build(int $submissionId, int $userGroupId, int $userId, ?bool $recommendOnly = null, ?bool $canChangeMetadata = null): StageAssignment
     {
         // Set defaults
-        $canChangeMetadata ??= Repo::userGroup()->get($userGroupId)->getPermitMetadataEdit();
+        $canChangeMetadata ??= UserGroup::find($userGroupId)?->permitMetadataEdit ?? false;
         $recommendOnly ??= false;
 
         return StageAssignment::withSubmissionIds([$submissionId])
diff --git a/classes/stageAssignment/StageAssignment.php b/classes/stageAssignment/StageAssignment.php
index 04da0d97002..315d50e9e1c 100644
--- a/classes/stageAssignment/StageAssignment.php
+++ b/classes/stageAssignment/StageAssignment.php
@@ -27,7 +27,10 @@
 use Illuminate\Database\Eloquent\Casts\Attribute;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use PKP\userGroup\relationships\UserGroupStage;
+use PKP\userGroup\UserGroup;
+use PKP\user\User;
 
 class StageAssignment extends Model
 {
@@ -55,6 +58,16 @@ public function userGroupStages(): HasMany
         return $this->hasMany(UserGroupStage::class, 'user_group_id', 'user_group_id');
     }
 
+    public function userGroup(): BelongsTo
+    {
+        return $this->belongsTo(UserGroup::class, 'user_group_id', 'user_group_id');
+    }
+
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'user_id', 'user_id');
+    }
+
     // Accessors and Mutators
 
     /**
diff --git a/classes/submission/Repository.php b/classes/submission/Repository.php
index 2538f515656..0adb80d6925 100644
--- a/classes/submission/Repository.php
+++ b/classes/submission/Repository.php
@@ -42,6 +42,7 @@
 use PKP\user\User;
 use PKP\validation\ValidatorFactory;
 use PKP\config\Config;
+use PKP\userGroup\UserGroup;
 
 abstract class Repository
 {
@@ -176,7 +177,11 @@ public function getWorkflowUrlByUserRoles(Submission $submission, ?int $userId =
         $dispatcher = $request->getDispatcher();
 
         // Check if the user is an author of this submission
-        $authorUserGroupIds = Repo::userGroup()->getArrayIdByRoleId(Role::ROLE_ID_AUTHOR);
+        $authorUserGroupIds = UserGroup::withContextIds([$submission->getData('contextId')])
+            ->withRoleIds([Role::ROLE_ID_AUTHOR])
+            ->get()
+            ->map(fn($userGroup) => $userGroup->id)
+            ->toArray();
 
         // Replaces StageAssignmentDAO::getBySubmissionAndStageId
         $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
@@ -187,6 +192,7 @@ public function getWorkflowUrlByUserRoles(Submission $submission, ?int $userId =
         foreach ($stageAssignments as $stageAssignment) {
             if (in_array($stageAssignment->userGroupId, $authorUserGroupIds)) {
                 $authorDashboard = true;
+                break;
             }
         }
 
diff --git a/classes/submission/maps/Schema.php b/classes/submission/maps/Schema.php
index 0924f1915f1..049a83cbcc7 100644
--- a/classes/submission/maps/Schema.php
+++ b/classes/submission/maps/Schema.php
@@ -540,12 +540,12 @@ function (Role $role) {
                     ->withStageIds([$stageId])
                     ->get();
 
-                foreach ($stageAssignments as $stageAssignment) {
-                    $userGroup = $this->getUserGroup($stageAssignment->userGroupId);
-                    if ($userGroup) {
-                        $currentUserAssignedRoles[] = $userGroup->getRoleId();
+                    foreach ($stageAssignments as $stageAssignment) {
+                        $userGroup = $this->getUserGroup($stageAssignment->userGroupId);
+                        if ($userGroup) {
+                            $currentUserAssignedRoles[] = $userGroup->roleId;
+                        }
                     }
-                }
 
                 // Replaces StageAssignmentDAO::getBySubmissionAndUserIdAndStageId
                 $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
@@ -554,9 +554,9 @@ function (Role $role) {
 
                 // FIXME - $stageAssignments are just temporarly added until https://github.com/pkp/pkp-lib/issues/10480 is ready
                 foreach ($stageAssignments as $stageAssignment) {
-                    $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
+                    $userGroup = UserGroup::find($stageAssignment->userGroupId);
                     $stageAssignmentsOverview[] = [
-                        "roleId" => $userGroup->getRoleId(),
+                        "roleId" => $userGroup?->roleId ?? null,
                         "recommendOnly" => $stageAssignment->recommendOnly,
                         "canChangeMetadata" => $stageAssignment->canChangeMetadata,
                         "userId" => $stageAssignment->userId
@@ -670,9 +670,8 @@ protected function getPropertyStageAssignments(Enumerable $stageAssignments): bo
 
     protected function getUserGroup(int $userGroupId): ?UserGroup
     {
-        /** @var UserGroup $userGroup */
         foreach ($this->userGroups as $userGroup) {
-            if ($userGroup->getId() === $userGroupId) {
+            if ($userGroup->id === $userGroupId) {
                 return $userGroup;
             }
         }
diff --git a/classes/submission/reviewer/ReviewerAction.php b/classes/submission/reviewer/ReviewerAction.php
index 9b00d21a067..82718cd60e5 100644
--- a/classes/submission/reviewer/ReviewerAction.php
+++ b/classes/submission/reviewer/ReviewerAction.php
@@ -133,18 +133,20 @@ public function getResponseEmail(
 
         // Get editorial contact name
         // Replaces StageAssignmentDAO::getBySubmissionAndStageId
-        $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
+        // Eager loading 'userGroup' and 'user' relationships
+        $stageAssignments = StageAssignment::with(['userGroup', 'user'])
+            ->withSubmissionIds([$submission->getId()])
             ->withStageIds([$reviewAssignment->getStageId()])
             ->get();
 
         $recipients = [];
         foreach ($stageAssignments as $stageAssignment) {
-            $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
-            if (!in_array($userGroup->getRoleId(), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR])) {
+            $userGroup = $stageAssignment->userGroup;
+            if ($userGroup && !in_array($userGroup->roleId, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR])) {
                 continue;
             }
 
-            $recipients[] = Repo::user()->get($stageAssignment->userId);
+            $recipients[] = $stageAssignment->user;
         }
 
         // Create dummy user if no one assigned
diff --git a/classes/submission/reviewer/form/PKPReviewerReviewStep3Form.php b/classes/submission/reviewer/form/PKPReviewerReviewStep3Form.php
index 6250d1cfc81..101221aaf08 100644
--- a/classes/submission/reviewer/form/PKPReviewerReviewStep3Form.php
+++ b/classes/submission/reviewer/form/PKPReviewerReviewStep3Form.php
@@ -43,6 +43,7 @@
 use PKP\submission\reviewAssignment\ReviewAssignment;
 use PKP\submission\SubmissionComment;
 use PKP\submission\SubmissionCommentDAO;
+use PKP\userGroup\UserGroup;
 
 class PKPReviewerReviewStep3Form extends ReviewerReviewForm
 {
@@ -169,72 +170,71 @@ public function execute(...$functionParams)
             'recommendation' => (int) $this->getData('recommendation'), // assign the recommendation to the review assignment, if there was one.
         ]);
 
-        // Replaces StageAssignmentDAO::getBySubmissionAndStageId
+        // Retrieve stage assignments for managers and sub-editors
         $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
             ->withStageIds([$submission->getData('stageId')])
+            ->whereHas('userGroup', function ($query) {
+                $query->withRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR]);
+            })
             ->get();
 
-        $receivedList = []; // Avoid sending twice to the same user.
-
-        /** @var NotificationSubscriptionSettingsDAO $notificationSubscriptionSettingsDao */
-        $notificationSubscriptionSettingsDao = DAORegistry::getDAO('NotificationSubscriptionSettingsDAO');
+        $receivedList = [];
+        // get the NotificationSubscriptionSettingsDAO
+        $notificationSubscriptionSettingsDao = DAORegistry::getDAO('NotificationSubscriptionSettingsDAO'); /** @var NotificationSubscriptionSettingsDAO $notificationSubscriptionSettingsDao */
+    
         foreach ($stageAssignments as $stageAssignment) {
             $userId = $stageAssignment->userId;
-            $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
-
-            // Never send reviewer comment notification to users other than managers and editors.
-            if (!in_array($userGroup->getRoleId(), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR]) || in_array($userId, $receivedList)) {
+            if (in_array($userId, $receivedList)) {
                 continue;
             }
-
-            // Notify editors
-            $notification = $notificationMgr->createNotification(
-                Application::get()->getRequest(),
+            $notificationType = Notification::NOTIFICATION_TYPE_REVIEWER_COMMENT;
+            $contextId = $context->getId();
+            // retrieve blocked email notifications for the user
+            $blockedEmailNotifications = $notificationSubscriptionSettingsDao->getNotificationSubscriptionSettings(
+                NotificationSubscriptionSettingsDAO::BLOCKED_EMAIL_NOTIFICATION_KEY,
                 $userId,
-                Notification::NOTIFICATION_TYPE_REVIEWER_COMMENT,
-                $submission->getData('contextId'),
-                PKPApplication::ASSOC_TYPE_REVIEW_ASSIGNMENT,
-                $reviewAssignment->getId()
+                $contextId
             );
 
-            // Check if user is subscribed to this type of notification emails
-            if (!$notification || in_array(
-                Notification::NOTIFICATION_TYPE_REVIEWER_COMMENT,
-                $notificationSubscriptionSettingsDao->getNotificationSubscriptionSettings(
-                    NotificationSubscriptionSettingsDAO::BLOCKED_EMAIL_NOTIFICATION_KEY,
+            // check if the user has blocked this notification type
+            if (!in_array($notificationType, $blockedEmailNotifications)) {
+                // Notify editors
+                $notification = $notificationMgr->createNotification(
+                    Application::get()->getRequest(),
                     $userId,
-                    (int) $context->getId()
-                )
-            )
-            ) {
-                continue;
-            }
+                    $notificationType,
+                    $submission->getData('contextId'),
+                    PKPApplication::ASSOC_TYPE_REVIEW_ASSIGNMENT,
+                    $reviewAssignment->getId()
+                );
+
+                if ($notification) {
+                    $mailable = new ReviewCompleteNotifyEditors($context, $submission, $reviewAssignment);
+                    $template = Repo::emailTemplate()->getByKey($context->getId(), ReviewCompleteNotifyEditors::getEmailTemplateKey());
+
+                    if (!$template) {
+                        $template = Repo::emailTemplate()->getByKey($context->getId(), 'NOTIFICATION');
+                        $request = Application::get()->getRequest();
+                        $mailable->addData([
+                            'notificationContents' => $notificationMgr->getNotificationContents($request, $notification),
+                            'notificationUrl' => $notificationMgr->getNotificationUrl($request, $notification),
+                        ]);
+                    }
 
-            $mailable = new ReviewCompleteNotifyEditors($context, $submission, $reviewAssignment);
-            $template = Repo::emailTemplate()->getByKey($context->getId(), ReviewCompleteNotifyEditors::getEmailTemplateKey());
-
-            // The template may not exist, see pkp/pkp-lib#9109
-            if (!$template) {
-                $template = Repo::emailTemplate()->getByKey($context->getId(), 'NOTIFICATION');
-                $request = Application::get()->getRequest();
-                $mailable->addData([
-                    'notificationContents' => $notificationMgr->getNotificationContents($request, $notification),
-                    'notificationUrl' => $notificationMgr->getNotificationUrl($request, $notification),
-                ]);
+                    $user = Repo::user()->get($userId);
+                    $mailable
+                        ->from($context->getData('contactEmail'), $context->getData('contactName'))
+                        ->recipients([$user])
+                        ->subject($template->getLocalizedData('subject'))
+                        ->body($template->getLocalizedData('body'))
+                        ->allowUnsubscribe($notification); // include unsubscribe link
+    
+                    Mail::send($mailable);
+                    Repo::emailLogEntry()->logMailable(SubmissionEmailLogEventType::REVIEW_COMPLETE, $mailable, $submission, $user);
+    
+                    $receivedList[] = $userId;
+                }
             }
-
-            $user = Repo::user()->get($userId);
-            $mailable
-                ->from($context->getData('contactEmail'), $context->getData('contactName'))
-                ->recipients([$user])
-                ->subject($template->getLocalizedData('subject'))
-                ->body($template->getLocalizedData('body'))
-                ->allowUnsubscribe($notification);
-
-            Mail::send($mailable);
-            Repo::emailLogEntry()->logMailable(SubmissionEmailLogEventType::REVIEW_COMPLETE, $mailable, $submission, $user);
-
-            $receivedList[] = $userId;
         }
 
         // Remove the task
diff --git a/classes/submissionFile/Repository.php b/classes/submissionFile/Repository.php
index 5d859a0afc9..4bd6a02bc98 100644
--- a/classes/submissionFile/Repository.php
+++ b/classes/submissionFile/Repository.php
@@ -311,7 +311,7 @@ public function add(SubmissionFile $submissionFile): int
                 ->withRoleIds([Role::ROLE_ID_AUTHOR])
                 ->withStageIds([$reviewRound->getStageId()])
                 ->get()
-                ->pluck('userId')
+                ->pluck('user_id')
                 ->all();
 
             $notificationMgr = new NotificationManager();
@@ -436,7 +436,7 @@ public function delete(SubmissionFile $submissionFile): void
                 $authorUserIds = StageAssignment::withSubmissionIds([$submissionFile->getData('submissionId')])
                     ->withRoleIds([Role::ROLE_ID_AUTHOR])
                     ->get()
-                    ->pluck('userId')
+                    ->pluck('user_id')
                     ->all();
 
                 $notificationMgr->updateNotification(
diff --git a/classes/template/PKPTemplateManager.php b/classes/template/PKPTemplateManager.php
index d21963db271..954af9e2448 100644
--- a/classes/template/PKPTemplateManager.php
+++ b/classes/template/PKPTemplateManager.php
@@ -62,6 +62,7 @@
 use PKP\submissionFile\SubmissionFile;
 use Smarty;
 use Smarty_Internal_Template;
+use PKP\userGroup\UserGroup;
 
 require_once('./lib/pkp/lib/vendor/smarty/smarty/libs/plugins/modifier.escape.php'); // Seems to be needed?
 
@@ -1325,11 +1326,24 @@ public function display($template = null, $cache_id = null, $compile_id = null,
         if (Application::isInstalled()) {
             $user = $this->_request->getUser();
             if ($user) {
-                $userGroups = Repo::userGroup()->userUserGroups($user->getId());
-
+                // Fetch user groups where the user is assigned
+                $userGroups = UserGroup::query()
+                    ->whereHas('userUserGroups', function ($query) use ($user) {
+                        $query->where('user_id', $user->getId())
+                            ->where(function ($q) {
+                                $q->whereNull('date_end')
+                                  ->orWhere('date_end', '>', now());
+                            })
+                            ->where(function ($q) {
+                                $q->whereNull('date_start')
+                                  ->orWhere('date_start', '<=', now());
+                            });
+                    })
+                    ->get();
+        
                 $userRoles = [];
                 foreach ($userGroups as $userGroup) {
-                    $userRoles[] = (int) $userGroup->getRoleId();
+                    $userRoles[] = (int) $userGroup->role_id;
                 }
                 $currentUser = [
                     'csrfToken' => $this->_request->getSession()->token(),
diff --git a/classes/user/Report.php b/classes/user/Report.php
index 7adfe007c57..f2401583083 100644
--- a/classes/user/Report.php
+++ b/classes/user/Report.php
@@ -79,7 +79,7 @@ private function _getHeadings(): array
             __('common.mailingAddress'),
             __('user.dateRegistered'),
             __('common.updated'),
-            ...array_map(fn (UserGroup $userGroup) => $userGroup->getLocalizedName(), $this->_getUserGroups())
+            ...array_map(fn (UserGroup $userGroup) => $userGroup->getLocalizedData('name'), $this->_getUserGroups())
         ];
     }
 
@@ -90,11 +90,23 @@ private function _getHeadings(): array
      */
     private function _getDataRow(User $user): array
     {
-        $userGroups = Repo::userGroup()->userUserGroups($user->getId());
-        $groups = [];
-        foreach ($userGroups as $userGroup) {
-            $groups[$userGroup->getId()] = 0;
-        }
+        // fetch user groups where the user is assigned
+        $userGroups = UserGroup::query()
+            ->whereHas('userUserGroups', function ($query) use ($user) {
+                $query->where('user_id', $user->getId())
+                    ->where(function ($q) {
+                        $q->whereNull('date_end')
+                        ->orWhere('date_end', '>', now());
+                    })
+                    ->where(function ($q) {
+                        $q->whereNull('date_start')
+                        ->orWhere('date_start', '<=', now());
+                    });
+            })
+            ->get();
+
+        // get the IDs of the user's groups
+        $userGroupIds = $userGroups->pluck('user_group_id')->all();
 
         return [
             $user->getId(),
@@ -106,7 +118,10 @@ private function _getDataRow(User $user): array
             $user->getMailingAddress(),
             $user->getDateRegistered(),
             $user->getLocalizedData('dateProfileUpdated'),
-            ...array_map(fn (UserGroup $userGroup) => __(isset($groups[$userGroup->getId()]) ? 'common.yes' : 'common.no'), $this->_getUserGroups())
+            ...array_map(
+                fn (UserGroup $userGroup) => __(in_array($userGroup->user_group_id, $userGroupIds) ? 'common.yes' : 'common.no'),
+                $this->_getUserGroups()
+            )
         ];
     }
 
@@ -118,9 +133,8 @@ private function _getDataRow(User $user): array
     private function _getUserGroups(): array
     {
         static $cache;
-        return $cache ??= Repo::userGroup()->getCollector()
-            ->filterByContextIds([$this->_request->getContext()->getId()])
-            ->getMany()
+        return $cache ??= UserGroup::withContextIds([$this->_request->getContext()->getId()])
+            ->get()
             ->toArray();
     }
 }
diff --git a/classes/user/Repository.php b/classes/user/Repository.php
index a1ac4f02ef9..685c8cb47f2 100644
--- a/classes/user/Repository.php
+++ b/classes/user/Repository.php
@@ -29,6 +29,8 @@
 use PKP\security\RoleDAO;
 use PKP\stageAssignment\StageAssignment;
 use PKP\submission\SubmissionCommentDAO;
+use PKP\userGroup\relationships\UserUserGroup;
+
 
 class Repository
 {
@@ -225,15 +227,14 @@ public function getAccessibleWorkflowStages(int $userId, int $contextId, Submiss
 
         $accessibleWorkflowStages = [];
         // Replaces StageAssignmentDAO::getBySubmissionAndUserIdAndStageId
-        $stageAssignments = StageAssignment::with(['userGroupStages'])
+        $stageAssignments = StageAssignment::with(['userGroup.userGroupStages'])
             ->withSubmissionIds([$submission->getId()])
             ->withUserId($userId)
             ->get();
-
-        // Assigned users have access based on their assignment
+        
         foreach ($stageAssignments as $stageAssignment) {
-            $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
-            $roleId = $userGroup->getRoleId();
+            $userGroup = $stageAssignment->userGroup;
+            $roleId = $userGroup->roleId;
 
             // Check global user roles within the context, e.g., user can be assigned in the role, which was revoked
             if (!in_array($roleId, $userRoleIds)) {
@@ -361,15 +362,33 @@ public function mergeUsers(int $oldUserId, int $newUserId)
         $subEditorsDao->deleteByUserId($oldUserId);
 
         // Transfer old user's roles
-        $userGroups = Repo::userGroup()->userUserGroups($oldUserId);
-        foreach ($userGroups as $userGroup) {
-            if (!Repo::userGroup()->userInGroup($newUserId, $userGroup->getId())) {
-                $mastheadStatus = Repo::userGroup()->getUserUserGroupMastheadStatus($oldUserId, $userGroup->getId());
-                Repo::userGroup()->assignUserToGroup($newUserId, $userGroup->getId(), null, null, $mastheadStatus);
+        $userUserGroups = UserUserGroup::query()
+            ->withUserId($oldUserId)
+            ->get();
+
+        // Transfer assignments to the new user
+        foreach ($userUserGroups as $userUserGroup) {
+            // Check if the new user is already assigned to this user group
+            $exists = UserUserGroup::query()
+                ->withUserId($newUserId)
+                ->withUserGroupId($userUserGroup->userGroupId)
+                ->exists();
+        
+            if (!$exists) {
+                UserUserGroup::create([
+                    'userId' => $newUserId,
+                    'userGroupId' => $userUserGroup->userGroupId,
+                    'dateStart' => $userUserGroup->dateStart,
+                    'dateEnd' => $userUserGroup->dateEnd,
+                    'masthead' => $userUserGroup->masthead,
+                ]);
             }
         }
 
-        Repo::userGroup()->deleteAssignmentsByUserId($oldUserId);
+        // Delete all user group assignments for the old user
+        UserUserGroup::query()
+            ->withUserId($oldUserId)
+            ->delete();
 
         // Transfer stage assignments.
         $stageAssignments = StageAssignment::withUserId($oldUserId)->get();
diff --git a/classes/user/form/RegistrationForm.php b/classes/user/form/RegistrationForm.php
index ec31b730d9e..321e33564f9 100644
--- a/classes/user/form/RegistrationForm.php
+++ b/classes/user/form/RegistrationForm.php
@@ -34,6 +34,7 @@
 use PKP\site\Site;
 use PKP\user\InterestManager;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 class RegistrationForm extends Form
 {
@@ -204,13 +205,16 @@ public function validate($callHooks = true)
             }
 
             if (!Config::getVar('general', 'sitewide_privacy_statement')) {
-                $contextIds = [];
-                foreach ($this->getData('userGroupIds') as $userGroupId) {
-                    $userGroup = Repo::userGroup()->get($userGroupId);
-                    $contextIds[] = $userGroup->getContextId();
-                }
-
-                $contextIds = array_unique($contextIds);
+                $userGroupIds = $this->getData('userGroupIds');
+    
+                // Fetch all user groups in a single query
+                $userGroups = UserGroup::query()->withUserGroupIds($userGroupIds)->get();
+    
+                // Collect context IDs using the 'map' method
+                $contextIds = $userGroups->map(function ($userGroup) {
+                    return $userGroup->contextId;
+                })->unique()->toArray();
+    
                 if (!empty($contextIds)) {
                     $contextDao = Application::getContextDao();
                     $privacyConsent = (array) $this->getData('privacyConsent');
diff --git a/classes/user/form/RolesForm.php b/classes/user/form/RolesForm.php
index 3989b8d275f..0a8520d3e43 100644
--- a/classes/user/form/RolesForm.php
+++ b/classes/user/form/RolesForm.php
@@ -21,6 +21,7 @@
 use APP\template\TemplateManager;
 use PKP\user\InterestManager;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 class RolesForm extends BaseProfileForm
 {
@@ -43,10 +44,8 @@ public function fetch($request, $template = null, $display = false)
     {
         $templateMgr = TemplateManager::getManager($request);
 
-        $userGroupIds = Repo::userGroup()->getCollector()
-            ->filterByUserIds([$request->getUser()->getId()])
-            ->getIds()
-            ->toArray();
+        $userGroupIds = UserGroup::getIdsByUserId($request->getUser()->getId());
+
 
         $templateMgr->assign('userGroupIds', $userGroupIds);
 
diff --git a/classes/user/form/UserFormHelper.php b/classes/user/form/UserFormHelper.php
index bcca06406ca..cd43b4bd813 100644
--- a/classes/user/form/UserFormHelper.php
+++ b/classes/user/form/UserFormHelper.php
@@ -106,11 +106,11 @@ public function saveRoleContent($form, $user)
                 $groupFormData = (array) $form->getData($groupData['formElement']);
                 $userGroups = Repo::userGroup()->getByRoleIds([$groupData['roleId']], $context->getId());
                 foreach ($userGroups as $userGroup) {
-                    if (!$userGroup->getPermitSelfRegistration()) {
+                    if (!$userGroup->permitSelfRegistration) {
                         continue;
                     }
 
-                    $groupId = $userGroup->getId();
+                    $groupId = $userGroup->id;
                     $inGroup = Repo::userGroup()->userInGroup($user->getId(), $groupId);
                     if (!$inGroup && array_key_exists($groupId, $groupFormData)) {
                         Repo::userGroup()->assignUserToGroup($user->getId(), $groupId);
diff --git a/classes/user/maps/Schema.php b/classes/user/maps/Schema.php
index 30e960bc97e..583e5e492e1 100644
--- a/classes/user/maps/Schema.php
+++ b/classes/user/maps/Schema.php
@@ -22,7 +22,8 @@
 use PKP\stageAssignment\StageAssignment;
 use PKP\user\User;
 use PKP\workflow\WorkflowStageDAO;
-use Submission;
+use APP\submission\Submission;
+use PKP\userGroup\UserGroup;
 
 class Schema extends \PKP\core\maps\Schema
 {
@@ -153,18 +154,26 @@ protected function mapByProperties(array $props, User $user, array $auxiliaryDat
                 case 'groups':
                     $output[$prop] = null;
                     if ($this->context) {
-                        $userGroups = Repo::userGroup()->userUserGroups($user->getId(), $this->context->getId());
+                        // Fetch user groups where the user is assigned in the current context
+                        $userGroups = UserGroup::query()
+                            ->withContextIds($this->context->getId())
+                            ->whereHas('userUserGroups', function ($query) use ($user) {
+                                $query->withUserId($user->getId())
+                                    ->withActive();
+                            })
+                            ->get();
+
                         $output[$prop] = [];
                         foreach ($userGroups as $userGroup) {
                             $output[$prop][] = [
-                                'id' => (int) $userGroup->getId(),
-                                'name' => $userGroup->getName(null),
-                                'abbrev' => $userGroup->getAbbrev(null),
-                                'roleId' => (int) $userGroup->getRoleId(),
-                                'showTitle' => (bool) $userGroup->getShowTitle(),
-                                'permitSelfRegistration' => (bool) $userGroup->getPermitSelfRegistration(),
-                                'permitMetadataEdit' => (bool) $userGroup->getPermitMetadataEdit(),
-                                'recommendOnly' => (bool) $userGroup->getRecommendOnly(),
+                                'id' => (int) $userGroup->id,
+                                'name' => $userGroup->getLocalizedData('name'),
+                                'abbrev' => $userGroup->getLocalizedData('abbrev'),
+                                'roleId' => (int) $userGroup->roleId,
+                                'showTitle' => (bool) $userGroup->showTitle,
+                                'permitSelfRegistration' => (bool) $userGroup->permitSelfRegistration,
+                                'permitMetadataEdit' => (bool) $userGroup->permitMetadataEdit,
+                                'recommendOnly' => (bool) $userGroup->recommendOnly,
                             ];
                         }
                     }
@@ -188,38 +197,47 @@ protected function mapByProperties(array $props, User $user, array $auxiliaryDat
                     }
                     break;
                 case 'stageAssignments':
-                    $submission = $auxiliaryData['submission'];
-                    $stageId = $auxiliaryData['stageId'];
+                    $submission = $auxiliaryData['submission'] ?? null;
+                    $stageId = $auxiliaryData['stageId'] ?? null;
 
-                    if((!isset($submission) || !isset($stageId)) || (!($submission instanceof Submission) || !is_numeric($auxiliaryData['stageId']))) {
+                    if (
+                        !($submission instanceof Submission) ||
+                        !is_numeric($stageId)
+                    ) {
                         $output['stageAssignments'] = [];
                         break;
                     }
 
                     // Get User's stage assignments for submission.
-                    // Note:
-                    // - A User can potentially have multiple assignments for a submission.
-                    // - A User can potentially have multiple assignments for a stage of a submission.
-                    $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
-                        ->withStageIds($stageId ? [$stageId] : [])
+                    $stageAssignments = StageAssignment::with(['userGroup'])
+                        ->withSubmissionIds([$submission->getId()])
+                        ->withStageIds([$stageId])
                         ->withUserId($user->getId())
                         ->withContextId($this->context->getId())
                         ->get();
 
                     $results = [];
 
-                    foreach ($stageAssignments as  $stageAssignment /**@var StageAssignment  $stageAssignment*/) {
-                        // Get related user group info for stage assignment
-                        $userGroup = Repo::userGroup()->get($stageAssignment->userGroupId);
+                    foreach ($stageAssignments as $stageAssignment) {
+                        $userGroup = $stageAssignment->userGroup;
 
                         // Only prepare data for non-reviewer participants
-                        if ($userGroup->getRoleId() !== Role::ROLE_ID_REVIEWER) {
+                        if ($userGroup && $userGroup->roleId !== Role::ROLE_ID_REVIEWER) {
                             $entry = [
                                 'stageAssignmentId' => $stageAssignment->id,
-                                'stageAssignmentUserGroup' => $userGroup->getAllData(),
+                                'stageAssignmentUserGroup' => [
+                                    'id' => (int) $userGroup->id,
+                                    'name' => $userGroup->getLocalizedData('name'),
+                                    'abbrev' => $userGroup->getLocalizedData('abbrev'),
+                                    'roleId' => (int) $userGroup->roleId,
+                                    'showTitle' => (bool) $userGroup->showTitle,
+                                    'permitSelfRegistration' => (bool) $userGroup->permitSelfRegistration,
+                                    'permitMetadataEdit' => (bool) $userGroup->permitMetadataEdit,
+                                    'recommendOnly' => (bool) $userGroup->recommendOnly,
+                                ],
                                 'stageAssignmentStageId' => $stageId,
-                                'recommendOnly' => (bool)$stageAssignment->recommendOnly,
-                                'canChangeMetadata' => (bool)$stageAssignment->canChangeMetadata
+                                'recommendOnly' => (bool) $stageAssignment->recommendOnly,
+                                'canChangeMetadata' => (bool) $stageAssignment->canChangeMetadata,
                             ];
 
                             $workflowStageDao = DAORegistry::getDAO('WorkflowStageDAO'); /** @var WorkflowStageDAO $workflowStageDao */
@@ -230,22 +248,20 @@ protected function mapByProperties(array $props, User $user, array $auxiliaryDat
 
                             $results[] = $entry;
                         }
-
-                        $output['stageAssignments'] = $results;
                     }
 
+                    $output['stageAssignments'] = $results;
                     break;
                 default:
                     $output[$prop] = $user->getData($prop);
                     break;
             }
+        }
+        $output = $this->schemaService->addMissingMultilingualValues($this->schema, $output, $this->context->getSupportedFormLocales());
 
-            $output = $this->schemaService->addMissingMultilingualValues($this->schema, $output, $this->context->getSupportedFormLocales());
-
-            Hook::call('UserSchema::getProperties::values', [$this, &$output, $user, $props]);
+        Hook::call('UserSchema::getProperties::values', [$this, &$output, $user, $props]);
 
-            ksort($output);
-        }
+        ksort($output);
 
         return $output;
     }
diff --git a/classes/userGroup/Collector.php b/classes/userGroup/Collector.php
deleted file mode 100644
index 63ac1c4749a..00000000000
--- a/classes/userGroup/Collector.php
+++ /dev/null
@@ -1,364 +0,0 @@
-<?php
-/**
- * @file classes/userGroup/Collector.php
- *
- * Copyright (c) 2014-2021 Simon Fraser University
- * Copyright (c) 2000-2021 John Willinsky
- * Distributed under the GNU GPL v3. For full terms see the file docs/COPYING.
- *
- * @class \PKP\userGroup\Collector
- *
- * @brief A helper class to configure a Query Builder to get a collection of userGroups
- */
-
-namespace PKP\userGroup;
-
-use Illuminate\Database\Query\Builder;
-use Illuminate\Support\Collection;
-use Illuminate\Support\Facades\DB;
-use Illuminate\Support\LazyCollection;
-use PKP\core\Core;
-use PKP\core\interfaces\CollectorInterface;
-use PKP\core\PKPApplication;
-use PKP\plugins\Hook;
-use PKP\userGroup\relationships\enums\UserUserGroupStatus;
-
-/**
- * @template T of UserGroup
- */
-class Collector implements CollectorInterface
-{
-    public const ORDERBY_ROLE_ID = 'roleId';
-    public const ORDERBY_ID = 'id';
-
-    public ?string $orderBy = self::ORDERBY_ID;
-
-    /** @var DAO */
-    public $dao;
-
-    public ?array $userGroupIds = null;
-
-    public ?array $contextIds = null; // getByContextId,
-
-    public ?array $roleIds = null;
-
-    public ?array $excludeRoles = null;
-
-    public ?array $stageIds = null; // getUserGroupsByStage
-
-    public ?array $publicationIds = null;
-
-    public ?bool $isDefault = null;
-
-    public ?bool $isRecommendOnly = null; // getRecommendOnlyGroupIds
-
-    public ?bool $permitSelfRegistration = null; // getRecommendOnlyGroupIds
-
-    public ?bool $permitMetadataEdit = null;
-
-    public ?bool $showTitle = null; // getPermitMetadataEditGroupIds
-
-    public ?array $userIds = null;
-
-    public ?int $count = null;
-
-    public ?int $offset = null;
-
-    public UserUserGroupStatus $userUserGroupStatus = UserUserGroupStatus::STATUS_ACTIVE;
-
-    public ?bool $masthead = null;
-
-
-    public function __construct(DAO $dao)
-    {
-        $this->dao = $dao;
-    }
-
-    public function getCount(): int
-    {
-        return $this->dao->getCount($this);
-    }
-
-    /**
-     * @return Collection<int,int>
-     */
-    public function getIds(): Collection
-    {
-        return $this->dao->getIds($this);
-    }
-
-    /**
-     * @copydoc DAO::getMany()
-     *
-     * @return LazyCollection<int,T>
-     */
-    public function getMany(): LazyCollection
-    {
-        return $this->dao->getMany($this);
-    }
-
-    /**
-     * Filter by multiple ids
-     */
-    public function filterByUserGroupIds(?array $ids): self
-    {
-        $this->userGroupIds = $ids;
-        return $this;
-    }
-
-    /**
-     * Filter by context IDs
-     */
-    public function filterByContextIds(?array $contextIds): self
-    {
-        $this->contextIds = $contextIds;
-        return $this;
-    }
-
-    /**
-     * Filter by publication IDs
-     */
-    public function filterByPublicationIds(?array $publicationIds): self
-    {
-        $this->publicationIds = $publicationIds;
-        return $this;
-    }
-
-    /**
-     * Filter by roles
-     */
-    public function filterByRoleIds(?array $roleIds): self
-    {
-        $this->roleIds = $roleIds;
-        return $this;
-    }
-
-    /**
-     * Exclude roles
-     */
-    public function filterExcludeRoles(?array $excludedRoles): self
-    {
-        $this->excludeRoles = $excludedRoles;
-        return $this;
-    }
-
-    /**
-     * Filter by contexts
-     */
-    public function filterByStageIds(?array $stageIds): self
-    {
-        $this->stageIds = $stageIds;
-        return $this;
-    }
-
-    /**
-     * Filter by is default
-     */
-    public function filterByIsDefault(?bool $isDefault): self
-    {
-        $this->isDefault = $isDefault;
-        return $this;
-    }
-
-    /**
-     * Filter by show title
-     */
-    public function filterByShowTitle(?bool $showTitle): self
-    {
-        $this->showTitle = $showTitle;
-        return $this;
-    }
-
-    /**
-     * Filter by permit self registration
-     */
-    public function filterByPermitSelfRegistration(?bool $permitSelfRegistration): self
-    {
-        $this->permitSelfRegistration = $permitSelfRegistration;
-        return $this;
-    }
-
-    /**
-     * Filter by permit metadata edit
-     */
-    public function filterByPermitMetadataEdit(?bool $permitMetadataEdit): self
-    {
-        $this->permitMetadataEdit = $permitMetadataEdit;
-        return $this;
-    }
-
-    /**
-     * Filter by masthead
-     */
-    public function filterByMasthead(?bool $masthead): self
-    {
-        $this->masthead = $masthead;
-        return $this;
-    }
-
-    /**
-     * Filter by permit metadata edit
-     */
-    public function filterByIsRecommendOnly(): self
-    {
-        $this->isRecommendOnly = true;
-        return $this;
-    }
-
-    /**
-     * Filter by user ids
-     */
-    public function filterByUserIds(?array $userIds): self
-    {
-        $this->userIds = $userIds;
-        return $this;
-    }
-
-    /**
-     * Filter by user's role status
-     */
-    public function filterByUserUserGroupStatus(UserUserGroupStatus $userUserGroupStatus): self
-    {
-        $this->userUserGroupStatus = $userUserGroupStatus;
-        return $this;
-    }
-
-    /**
-     * Include orderBy columns to the collector query
-     */
-    public function orderBy(?string $orderBy): self
-    {
-        $this->orderBy = $orderBy;
-        return $this;
-    }
-
-    /**
-     * Limit the number of objects retrieved
-     */
-    public function limit(?int $count): self
-    {
-        $this->count = $count;
-        return $this;
-    }
-
-    /**
-     * Offset the number of objects retrieved, for example to
-     * retrieve the second page of contents
-     */
-    public function offset(?int $offset): self
-    {
-        $this->offset = $offset;
-        return $this;
-    }
-
-    /**
-     * @copydoc CollectorInterface::getQueryBuilder()
-     *
-     * @hook UserGroup::Collector [[&$q, $this]]
-     */
-    public function getQueryBuilder(): Builder
-    {
-        $q = DB::table('user_groups as ug')
-            ->select('ug.*');
-
-        if (isset($this->userGroupIds)) {
-            $q->whereIn('ug.user_group_id', $this->userGroupIds);
-        }
-
-        if (isset($this->userIds)) {
-            $q->join('user_user_groups as uug', 'ug.user_group_id', '=', 'uug.user_group_id');
-            $q->whereIn('uug.user_id', $this->userIds);
-            $currentDateTime = Core::getCurrentDate();
-            if ($this->userUserGroupStatus === UserUserGroupStatus::STATUS_ENDED) {
-                $q->whereNotNull('uug.date_end')
-                    ->where('uug.date_end', '<=', $currentDateTime);
-            } elseif ($this->userUserGroupStatus === UserUserGroupStatus::STATUS_ACTIVE) {
-                $q->where(
-                    fn (Builder $q) =>
-                    $q->where('uug.date_start', '<=', $currentDateTime)
-                        ->orWhereNull('uug.date_start')
-                )
-                    ->where(
-                        fn (Builder $q) =>
-                        $q->where('uug.date_end', '>', $currentDateTime)
-                            ->orWhereNull('uug.date_end')
-                    );
-            }
-        }
-
-        if (isset($this->publicationIds)) {
-            $q->join('authors as a', 'a.user_group_id', '=', 'ug.user_group_id')
-                ->whereIn('a.publication_id', $this->publicationIds);
-        }
-
-        if (isset($this->stageIds)) {
-            $q->join('user_group_stage as ugs', function ($join) {
-                $join->on('ug.user_group_id', '=', 'ugs.user_group_id');
-                $join->on('ug.context_id', '=', 'ugs.context_id');
-            })->whereIn('ugs.stage_id', $this->stageIds);
-        }
-
-        if (isset($this->contextIds)) {
-            $q->whereIn(DB::raw('COALESCE(ug.context_id, 0)'), array_map(intval(...), $this->contextIds));
-        }
-
-        if (isset($this->roleIds)) {
-            $q->whereIn('ug.role_id', $this->roleIds);
-        }
-
-        if (isset($this->excludeRoles)) {
-            $q->whereNotIn('ug.role_id', $this->excludeRoles);
-        }
-
-        $q->when($this->isRecommendOnly !== null, function (Builder $q) {
-            $q->whereIn('ug.user_group_id', function (Builder $q) {
-                $q->select('user_group_id')
-                    ->from($this->dao->settingsTable)
-                    ->where('setting_name', '=', 'recommendOnly')
-                    ->where('setting_value', $this->isRecommendOnly);
-            });
-        });
-
-        $q->when($this->isDefault !== null, function (Builder $q) {
-            $q->where('ug.is_default', $this->isDefault ? 1 : 0);
-        });
-
-        $q->when($this->permitSelfRegistration !== null, function (Builder $q) {
-            $q->where('ug.permit_self_registration', $this->permitSelfRegistration ? 1 : 0);
-        });
-
-        $q->when($this->permitMetadataEdit !== null, function (Builder $q) {
-            $q->where('ug.permit_metadata_edit', $this->permitMetadataEdit ? 1 : 0);
-        });
-
-        $q->when($this->masthead !== null, function (Builder $q) {
-            $q->where('ug.masthead', $this->masthead ? 1 : 0);
-        });
-
-        $q->when($this->showTitle !== null, function (Builder $q) {
-            $q->where('ug.show_title', $this->showTitle ? 1 : 0);
-        });
-
-        if (isset($this->count)) {
-            $q->limit($this->count);
-        }
-
-        if (isset($this->offset)) {
-            $q->offset($this->offset);
-        }
-
-        switch ($this->orderBy) {
-            case self::ORDERBY_ROLE_ID:
-                $q->orderBy('ug.role_id', 'asc');
-                break;
-            case self::ORDERBY_ID:
-                $q->orderBy('ug.user_group_id', 'asc');
-                break;
-        }
-
-        // Add app-specific query statements
-        Hook::call('UserGroup::Collector', [&$q, $this]);
-
-        return $q;
-    }
-}
diff --git a/classes/userGroup/DAO.php b/classes/userGroup/DAO.php
deleted file mode 100644
index dcf670c6efd..00000000000
--- a/classes/userGroup/DAO.php
+++ /dev/null
@@ -1,170 +0,0 @@
-<?php
-
-/**
- * @file classes/userGroup/DAO.php
- *
- * Copyright (c) 2014-2021 Simon Fraser University
- * Copyright (c) 2000-2021 John Willinsky
- * Distributed under the GNU GPL v3. For full terms see the file docs/COPYING.
- *
- * @class \PKP\userGroup\DAO
- *
- * @see \PKP\userGroup\UserGroup
- *
- * @brief Operations for retrieving and modifying UserGroup objects.
- */
-
-namespace PKP\userGroup;
-
-use APP\core\Application;
-use Illuminate\Database\Query\Builder;
-use Illuminate\Support\Collection;
-use Illuminate\Support\Facades\DB;
-use Illuminate\Support\LazyCollection;
-use PKP\core\Core;
-use PKP\core\EntityDAO;
-use PKP\core\PKPApplication;
-use PKP\core\traits\EntityWithParent;
-use PKP\services\PKPSchemaService;
-
-/**
- * @template T of UserGroup
- *
- * @extends EntityDAO<T>
- */
-class DAO extends EntityDAO
-{
-    use EntityWithParent;
-
-    /** @copydoc EntityDAO::$schema */
-    public $schema = PKPSchemaService::SCHEMA_USER_GROUP;
-
-    /** @copydoc EntityDAO::$table */
-    public $table = 'user_groups';
-
-    /** @copydoc EntityDAO::$settingsTable */
-    public $settingsTable = 'user_group_settings';
-
-    /** @copydoc EntityDAO::$primaryKeyColumn */
-    public $primaryKeyColumn = 'user_group_id';
-
-    /** @copydoc EntityDAO::$primaryTableColumns */
-    public $primaryTableColumns = [
-        'id' => 'user_group_id',
-        'contextId' => 'context_id',
-        'roleId' => 'role_id',
-        'isDefault' => 'is_default',
-        'showTitle' => 'show_title',
-        'permitSelfRegistration' => 'permit_self_registration',
-        'permitMetadataEdit' => 'permit_metadata_edit',
-        'masthead' => 'masthead',
-    ];
-
-    /**
-     * Get the parent object ID column name
-     */
-    public function getParentColumn(): string
-    {
-        return 'context_id';
-    }
-
-    /**
-     * Instantiate a new DataObject
-     */
-    public function newDataObject(): UserGroup
-    {
-        return app(UserGroup::class);
-    }
-
-    /**
-     * Get the total count of rows matching the configured query
-     */
-    public function getCount(Collector $query): int
-    {
-        return $query
-            ->getQueryBuilder()
-            ->getCountForPagination();
-    }
-
-    /**
-     * Get a list of ids matching the configured query
-     *
-     * @return Collection<int,int>
-     */
-    public function getIds(Collector $query): Collection
-    {
-        return $query
-            ->getQueryBuilder()
-            ->select('ug.' . $this->primaryKeyColumn)
-            ->pluck('ug.' . $this->primaryKeyColumn);
-    }
-
-    /**
-     * Get a collection of publications matching the configured query
-     *
-     * @return LazyCollection<int,T>
-     */
-    public function getMany(Collector $query): LazyCollection
-    {
-        $rows = $query
-            ->getQueryBuilder()
-            ->get();
-
-        return LazyCollection::make(function () use ($rows) {
-            foreach ($rows as $row) {
-                yield $row->user_group_id => $this->fromRow($row);
-            }
-        });
-    }
-
-    /**
-     * @copydoc EntityDAO::insert()
-     */
-    public function insert(UserGroup $userGroup): int
-    {
-        return parent::_insert($userGroup);
-    }
-
-    /**
-     * @copydoc EntityDAO::update()
-     */
-    public function update(UserGroup $userGroup)
-    {
-        parent::_update($userGroup);
-    }
-
-    /**
-     * @copydoc EntityDAO::delete()
-     */
-    public function delete(UserGroup $userGroup)
-    {
-        parent::_delete($userGroup);
-    }
-
-    /**
-     * Retrieves a keyed Collection (key = user_group_id, value = count) with the amount of active users for each user group
-     */
-    public function getUserCountByContextId(?int $contextId = Application::SITE_CONTEXT_ID_ALL): Collection
-    {
-        $currentDateTime = Core::getCurrentDate();
-        return DB::table('user_groups', 'ug')
-            ->join('user_user_groups AS uug', 'uug.user_group_id', '=', 'ug.user_group_id')
-            ->join('users AS u', 'u.user_id', '=', 'uug.user_id')
-            ->when($contextId !== Application::SITE_CONTEXT_ID_ALL, fn (Builder $query) => $query->whereRaw('COALESCE(ug.context_id, 0) = ?', [(int) $contextId]))
-            ->where('u.disabled', '=', 0)
-            ->where(
-                fn (Builder $q) =>
-                $q->where('uug.date_start', '<=', $currentDateTime)
-                    ->orWhereNull('uug.date_start')
-            )
-            ->where(
-                fn (Builder $q) =>
-                $q->where('uug.date_end', '>', $currentDateTime)
-                    ->orWhereNull('uug.date_end')
-            )
-            ->groupBy('ug.user_group_id')
-            ->select('ug.user_group_id')
-            ->selectRaw('COUNT(0) AS count')
-            ->pluck('count', 'user_group_id');
-    }
-}
diff --git a/classes/userGroup/Repository.php b/classes/userGroup/Repository.php
index dcaf172669d..62f63ab50bc 100644
--- a/classes/userGroup/Repository.php
+++ b/classes/userGroup/Repository.php
@@ -13,9 +13,6 @@
 
 namespace PKP\userGroup;
 
-use APP\core\Application;
-use APP\core\Request;
-use APP\facades\Repo;
 use Carbon\Carbon;
 use DateInterval;
 use Illuminate\Support\Collection;
@@ -23,7 +20,6 @@
 use Illuminate\Support\LazyCollection;
 use PKP\core\Core;
 use PKP\db\DAORegistry;
-use PKP\facades\Locale;
 use PKP\plugins\Hook;
 use PKP\security\Role;
 use PKP\services\PKPSchemaService;
@@ -34,7 +30,6 @@
 use PKP\userGroup\relationships\UserUserGroup;
 use PKP\validation\ValidatorFactory;
 use PKP\xml\PKPXMLParser;
-use stdClass;
 
 class Repository
 {
@@ -46,51 +41,46 @@ class Repository
     /** @var string Max lifetime for the Editorial Masthead and Editorial History users cache. */
     public const MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME = '1 year';
 
-    /** @var DAO */
-    public $dao;
-
     /** @var string $schemaMap The name of the class to map this entity to its schema */
     public $schemaMap = maps\Schema::class;
 
-    /** @var Request */
-    protected $request;
 
     /** @var PKPSchemaService<UserGroup> */
     protected $schemaService;
 
-    public function __construct(DAO $dao, Request $request, PKPSchemaService $schemaService)
+    public function __construct(PKPSchemaService $schemaService)
     {
-        $this->dao = $dao;
-        $this->request = $request;
         $this->schemaService = $schemaService;
     }
 
-    /** @copydoc DAO::newDataObject() */
-    public function newDataObject(array $params = []): UserGroup
-    {
-        $object = $this->dao->newDataObject();
-        if (!empty($params)) {
-            $object->setAllData($params);
-        }
-        return $object;
-    }
-
-    /** @copydoc DAO::get() */
+    /**
+     * Retrieve UserGroup by id and optional context id.
+     *
+     * @param int $id
+     * @param int|null $contextId
+     * @return UserGroup|null
+     */
     public function get(int $id, ?int $contextId = null): ?UserGroup
     {
-        return $this->dao->get($id, $contextId);
+        return UserGroup::findById($id, $contextId);
     }
 
-    /** @copydoc DAO::exists() */
+    /**
+     * Check if UserGroup exists by id and context id.
+     *
+     * @param int $id
+     * @param int|null $contextId
+     * @return bool
+     */
     public function exists(int $id, ?int $contextId = null): bool
     {
-        return $this->dao->exists($id, $contextId);
-    }
+        $query = UserGroup::query()->where('user_group_id', $id);
 
-    /** @copydoc DAO::getCollector() */
-    public function getCollector(): Collector
-    {
-        return app(Collector::class);
+        if ($contextId !== null) {
+            $query->withContextIds([$contextId]);
+        }
+
+        return $query->exists();
     }
 
     /**
@@ -148,335 +138,351 @@ public function validate($userGroup, $props, $allowedLocales, $primaryLocale)
         return $errors;
     }
 
-    public function add(UserGroup $userGroup): int
-    {
-        $userGroupId = $this->dao->insert($userGroup);
-        $userGroup = Repo::userGroup()->get($userGroupId);
-
-        Hook::call('UserGroup::add', [$userGroup]);
-
-        // Clear editorial masthead cache if the new role should be added to the masthead
-        // Because it is a new role, no need to clear editorial history chache
-        if ($userGroup->getMasthead()) {
-            self::forgetEditorialMastheadCache($userGroup->getContextId());
-        }
-        return $userGroup->getId();
-    }
-
-    public function edit(UserGroup $userGroup, array $params)
-    {
-        $newUserGroup = Repo::userGroup()->newDataObject(array_merge($userGroup->_data, $params));
-
-        Hook::call('UserGroup::edit', [$newUserGroup, $userGroup, $params]);
-
-        $this->dao->update($newUserGroup);
-
-        // Clear editorial masthead and history cache if the role is on the masthead
-        if ($userGroup->getMasthead()) {
-            self::forgetEditorialMastheadCache($userGroup->getContextId());
-            self::forgetEditorialHistoryCache($userGroup->getContextId());
-        }
-
-        Repo::userGroup()->get($newUserGroup->getId());
-    }
-
-    public function delete(UserGroup $userGroup)
-    {
-        Hook::call('UserGroup::delete::before', [$userGroup]);
-
-        $this->dao->delete($userGroup);
-
-        Hook::call('UserGroup::delete', [$userGroup]);
-    }
-
     /**
-    * Delete all user groups assigned to a certain context by contextId
-    */
-    public function deleteByContextId(int $contextId)
+     * Delete all user groups assigned to a certain context by contextId
+     *
+     * @param int $contextId
+     * @return void
+     */
+    public function deleteByContextId(int $contextId): void
     {
-        $userGroupIds = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$contextId])
-            ->getIds();
-
-        foreach ($userGroupIds as $userGroupId) {
-            $this->dao->deleteById($userGroupId);
-        }
+        UserGroup::query()
+            ->withContextIds([$contextId])
+            ->each(function (UserGroup $userGroup) {
+                $userGroup->delete();
+            });
     }
 
     /**
-    * Return all user group ids given a certain role id
-    *
-    * @param int $roleId
-    */
-    public function getArrayIdByRoleId($roleId, ?int $contextId = null): array
+     * Return all user group ids given a certain role ID and context id
+     *
+     * @param int $roleId
+     * @param int|null $contextId
+     * @return array
+     */
+    public function getArrayIdByRoleId(int $roleId, ?int $contextId = null): array
     {
-        $collector = Repo::userGroup()->getCollector()
-            ->filterByRoleIds([$roleId]);
+        $query = UserGroup::query()
+            ->withRoleIds([$roleId]);
 
-        if ($contextId) {
-            $collector->filterByContextIds([$contextId]);
+        if ($contextId !== null) {
+            $query->withContextIds([$contextId]);
         }
 
-        return $collector->getIds()->toArray();
+        return $query->pluck('user_group_id')->toArray();
     }
 
     /**
-    * Return all user group ids given a certain role id
-    *
-    * @param ?bool $default Give null for all user groups, else define whether it is default
-    *
-    * @return LazyCollection<int,UserGroup>
-    */
+     * Return all user groups given role ids, context id and default flag
+     *
+     * @param array $roleIds
+     * @param int $contextId
+     * @param bool|null $default
+     * @return LazyCollection<int, UserGroup>
+     */
     public function getByRoleIds(array $roleIds, int $contextId, ?bool $default = null): LazyCollection
     {
-        $collector = Repo::userGroup()
-            ->getCollector()
-            ->filterByRoleIds($roleIds)
-            ->filterByContextIds([$contextId])
-            ->filterByIsDefault($default);
+        $query = UserGroup::query()
+            ->withRoleIds($roleIds)
+            ->withContextIds([$contextId]);
+
+        if ($default !== null) {
+            $query->isDefault($default);
+        }
 
-        return $collector->getMany();
+        return $query->cursor();
     }
 
     /**
-    * Return all, active or ended user groups ids for a user id
-    *
-    * @return LazyCollection<int,UserGroup>
-    */
-    public function userUserGroups(int $userId, ?int $contextId = null, ?UserUserGroupStatus $userUserGroupStatus = UserUserGroupStatus::STATUS_ACTIVE): LazyCollection
+     * Return all active or ended user groups for a user id and context id (optional)
+     *
+     * @param int $userId
+     * @param int|null $contextId
+     * @param UserUserGroupStatus $status
+     * @return LazyCollection<int, UserGroup>
+     */
+    public function userUserGroups(int $userId, ?int $contextId = null, UserUserGroupStatus $status = UserUserGroupStatus::STATUS_ACTIVE): LazyCollection
     {
-        $collector = Repo::userGroup()
-            ->getCollector()
-            ->filterByUserIds([$userId])
-            ->filterByUserUserGroupStatus($userUserGroupStatus);
+        $query = UserGroup::query()
+            ->withUserIds([$userId])
+            ->withUserUserGroupStatus($status->value);
 
-        if ($contextId) {
-            $collector->filterByContextIds([$contextId]);
+        if ($contextId !== null) {
+            $query->withContextIds([$contextId]);
         }
 
-        return $collector->getMany();
+        return $query->cursor();
     }
 
     /**
-    * Return all context IDs for masthead user groups the given user is or was assigned to
-    *
-    * @return Collection of context IDs
-    */
+     * Return all context IDs for masthead user groups the given user is or was assigned to
+     *
+     * @param int $userId
+     * @return Collection
+     */
     public function getUserUserGroupsContextIds(int $userId): Collection
     {
-        return Repo::userGroup()
-            ->getCollector()
-            ->filterByUserIds([$userId])
-            ->filterByUserUserGroupStatus(UserUserGroupStatus::STATUS_ALL)
-            ->filterByMasthead(true)
-            ->getQueryBuilder()
+        return UserGroup::query()
+            ->withUserIds([$userId])
+            ->withUserUserGroupStatus(UserUserGroupStatus::STATUS_ALL->value)
+            ->masthead(true)
             ->pluck('context_id')
             ->unique();
     }
 
     /**
-    * return whether a user is in a user group
-    */
+     * Determine whether a user is in a specific user group
+     *
+     * @param int $userId
+     * @param int $userGroupId
+     * @return bool
+     */
     public function userInGroup(int $userId, int $userGroupId): bool
     {
-        return UserUserGroup::withUserId($userId)
+        return UserUserGroup::query()
+            ->withUserId($userId)
             ->withUserGroupId($userGroupId)
             ->withActive()
-            ->get()
-            ->isNotEmpty();
+            ->exists();
     }
 
     /**
-    * return whether an active user in a user group should be displayed on the masthead
-    */
-    public function userOnMasthead(int $userId, ?int $userGroupId): bool
+     * Determine whether an active user in a user group should be displayed on the masthead
+     *
+     * @param int $userId
+     * @param int|null $userGroupId
+     * @return bool
+     */
+    public function userOnMasthead(int $userId, ?int $userGroupId = null): bool
     {
         if ($userGroupId) {
-            $userGroup = Repo::userGroup()->get($userGroupId);
-            if (!$userGroup->getMasthead()) {
+            $userGroup = $this->get($userGroupId);
+            if (!$userGroup || !$userGroup->masthead) {
                 return false;
             }
         }
-        $query = UserUserGroup::withUserId($userId)
+
+        $query = UserUserGroup::query()
+            ->withUserId($userId)
             ->withActive()
             ->withMasthead();
+
         if ($userGroupId) {
             $query->withUserGroupId($userGroupId);
         }
-        return $query->get()->isNotEmpty();
+
+        return $query->exists();
     }
 
     /**
-     * Get user masthead status for a user group the user is currently active in
+     * Get UserUserGroup masthead status for a UserGroup the user is currently active in
+     *
+     * @param int $userId
+     * @param int $userGroupId
+     * @return UserUserGroupMastheadStatus
      */
     public function getUserUserGroupMastheadStatus(int $userId, int $userGroupId): UserUserGroupMastheadStatus
     {
-        $masthead = UserUserGroup::withUserId($userId)
+        $masthead = UserUserGroup::query()
+            ->withUserId($userId)
             ->withUserGroupId($userGroupId)
             ->withActive()
-            ->pluck('masthead');
-        switch ($masthead[0]) {
-            case 1:
-                return UserUserGroupMastheadStatus::STATUS_ON;
-            case 0:
-                return UserUserGroupMastheadStatus::STATUS_OFF;
-            case null:
-                return UserUserGroupMastheadStatus::STATUS_NULL;
-        }
+            ->pluck('masthead')
+            ->first();
+
+        return match ($masthead) {
+            true => UserUserGroupMastheadStatus::STATUS_ON,
+            false => UserUserGroupMastheadStatus::STATUS_OFF,
+            default => UserUserGroupMastheadStatus::STATUS_NULL,
+        };
     }
 
     /**
-    * return whether a context has a specific user group
-    */
+     * Determine whether a context has a specific UserGroup
+     *
+     * @param int $contextId
+     * @param int $userGroupId
+     * @return bool
+     */
     public function contextHasGroup(int $contextId, int $userGroupId): bool
     {
-        return Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$contextId])
-            ->filterByUserGroupIds([$userGroupId])
-            ->getCount() > 0;
+        return UserGroup::query()
+            ->withContextIds([$contextId])
+            ->withUserGroupIds([$userGroupId])
+            ->exists();
     }
 
     /**
-     * Assign a user to a role
+     * Assign a user to a UserGroup
      *
+     * @param int $userId
+     * @param int $userGroupId
      * @param string|null $startDate The date in ISO (YYYY-MM-DD HH:MM:SS) format
      * @param string|null $endDate The date in ISO (YYYY-MM-DD HH:MM:SS) format
+     * @param UserUserGroupMastheadStatus|null $mastheadStatus
+     * @return UserUserGroup|null
      */
-    public function assignUserToGroup(int $userId, int $userGroupId, ?string $startDate = null, ?string $endDate = null, ?UserUserGroupMastheadStatus $mastheadStatus = null): ?UserUserGroup
-    {
+    public function assignUserToGroup(
+        int $userId,
+        int $userGroupId,
+        ?string $startDate = null,
+        ?string $endDate = null,
+        ?UserUserGroupMastheadStatus $mastheadStatus = null
+    ): ?UserUserGroup {
         if ($endDate && !Carbon::parse($endDate)->isFuture()) {
             return null;
         }
 
         $dateStart = $startDate ?? Core::getCurrentDate();
-        $userGroup = Repo::userGroup()->get($userGroupId);
-        // user_user_group's masthead does not inherit from the user_group's masthead,
-        // it needs to be specified (when accepting an invitations).
-        switch ($mastheadStatus) {
-            case UserUserGroupMastheadStatus::STATUS_ON:
-                $masthead = 1;
-                break;
-            case UserUserGroupMastheadStatus::STATUS_OFF:
-                $masthead = 0;
-                break;
-            default:
-                $masthead = $userGroup->getMasthead() ? 1 : null;
+        $userGroup = UserGroup::find($userGroupId);
+
+        if (!$userGroup) {
+            return null;
         }
+
+        // Determine masthead status
+        $masthead = match ($mastheadStatus) {
+            UserUserGroupMastheadStatus::STATUS_ON => true,
+            UserUserGroupMastheadStatus::STATUS_OFF => false,
+            default => null,
+        };
+
         // Clear editorial masthead cache if a new user is assigned to a masthead role
-        if ($userGroup->getMasthead()) {
-            self::forgetEditorialMastheadCache($userGroup->getContextId());
+        if ($userGroup->masthead) {
+            self::forgetEditorialCache($userGroup->contextId);
         }
+
         return UserUserGroup::create([
-            'userId' => $userId,
-            'userGroupId' => $userGroupId,
-            'dateStart' => $dateStart,
-            'dateEnd' => $endDate,
+            'user_id' => $userId,
+            'user_group_id' => $userGroupId,
+            'date_start' => $dateStart,
+            'date_end' => $endDate,
             'masthead' => $masthead,
         ]);
     }
 
     /**
-     * Remove all user role assignments. This should be used only when merging i.e. fully deleting an user.
+     * Remove all user role assignments for a user. optionally within a specific UserGroup
+     *
+     * This should be used only when merging, i.e., fully deleting a user.
+     *
+     * @param int $userId
+     * @param int|null $userGroupId
+     * @return bool
      */
     public function deleteAssignmentsByUserId(int $userId, ?int $userGroupId = null): bool
     {
         if (!$userGroupId) {
             $contextIds = $this->getUserUserGroupsContextIds($userId);
             foreach ($contextIds as $contextId) {
-                self::forgetEditorialMastheadCache($contextId);
+                self::forgetEditorialCache($contextId);
                 self::forgetEditorialHistoryCache($contextId);
             }
         }
 
-        $query = UserUserGroup::withUserId($userId);
+        $query = UserUserGroup::query()->withUserId($userId);
 
         if ($userGroupId) {
             $query->withUserGroupId($userGroupId);
             $userGroup = $this->get($userGroupId);
-            if ($userGroup->getMasthead()) {
-                self::forgetEditorialMastheadCache($contextId);
-                self::forgetEditorialHistoryCache($contextId);
+            if ($userGroup && $userGroup->masthead) {
+                self::forgetEditorialCache($userGroup->contextId);
+                self::forgetEditorialHistoryCache($userGroup->contextId);
             }
         }
 
-        return $query->delete();
+        return $query->delete() > 0;
     }
 
+    /**
+     * End user assignments by setting the end date.
+     *
+     * @param int $contextId
+     * @param int $userId
+     * @param int|null $userGroupId
+     * @return void
+     */
     public function endAssignments(int $contextId, int $userId, ?int $userGroupId = null): void
     {
         // Clear editorial masthead and history cache if the user was displayed on the masthead for the given role
         if ($this->userOnMasthead($userId, $userGroupId)) {
-            self::forgetEditorialMastheadCache($contextId);
+            self::forgetEditorialCache($contextId);
             self::forgetEditorialHistoryCache($contextId);
         }
 
         $dateEnd = Core::getCurrentDate();
-        $query = UserUserGroup::withContextId($contextId)
+        $query = UserUserGroup::query()
+            ->withContextId($contextId)
             ->withUserId($userId)
             ->withActive();
+
         if ($userGroupId) {
             $query->withUserGroupId($userGroupId);
         }
+
         $query->update(['date_end' => $dateEnd]);
     }
 
     /**
-    * Get the user groups assigned to each stage.
-    *
-    * @param null|mixed $roleId
-    * @param null|mixed $count
-    *
-    * @return LazyCollection<int,UserGroup>
-    */
-    public function getUserGroupsByStage(int $contextId, $stageId, $roleId = null, $count = null): LazyCollection
+     * Get the user groups assigned to each stage.
+     *
+     * @param int $contextId
+     * @param int $stageId
+     * @param int|null $roleId
+     * @param int|null $count
+     * @return LazyCollection<int, UserGroup>
+     */
+    public function getUserGroupsByStage(int $contextId, int $stageId, ?int $roleId = null, ?int $count = null): LazyCollection
     {
-        $userGroups = $this->getCollector()
-            ->filterByContextIds([$contextId])
-            ->filterByStageIds([$stageId]);
+        $query = UserGroup::query()
+            ->withContextIds([$contextId])
+            ->withStageIds([$stageId]);
 
-        if ($roleId) {
-            $userGroups->filterByRoleIds([$roleId]);
+        if ($roleId !== null) {
+            $query->withRoleIds([$roleId]);
         }
 
-        $userGroups->orderBy(Collector::ORDERBY_ROLE_ID);
+        $query->orderByRoleId();
+
+        if ($count !== null) {
+            $query->limit($count);
+        }
 
-        return $userGroups->getMany();
+        return $query->cursor();
     }
 
     /**
-    * Remove a user group from a stage
-    */
+     * Remove a user group from a stage
+     *
+     * @param int $contextId
+     * @param int $userGroupId
+     * @param int $stageId
+     * @return bool
+     */
     public function removeGroupFromStage(int $contextId, int $userGroupId, int $stageId): bool
     {
-        return UserGroupStage::withContextId($contextId)
+        return UserGroupStage::query()
+            ->withContextId($contextId)
             ->withUserGroupId($userGroupId)
             ->withStageId($stageId)
-            ->delete();
+            ->delete() > 0;
     }
 
     /**
      * Get all stages assigned to one user group in one context.
      *
      * @param int $contextId The context ID.
-     * @param int $userGroupId The user group ID
-     *
+     * @param int $userGroupId The UserGroup ID
+     * @return Collection
      */
     public function getAssignedStagesByUserGroupId(int $contextId, int $userGroupId): Collection
     {
-        return UserGroupStage::withContextId($contextId)
+        return UserGroupStage::query()
+            ->withContextId($contextId)
             ->withUserGroupId($userGroupId)
             ->pluck('stage_id');
     }
 
-    /**
-     * Retrieves a keyed Collection (key = user_group_id, value = count) with the amount of active users for each user group
-     */
-    public function getUserCountByContextId(?int $contextId = null): Collection
-    {
-        return $this->dao->getUserCountByContextId($contextId);
-    }
-
     /**
      * Get the user group a new author may be assigned to
      * when they make their first submission, if they are
@@ -484,28 +490,27 @@ public function getUserCountByContextId(?int $contextId = null): Collection
      *
      * This returns the first user group with ROLE_ID_AUTHOR
      * that permits self-registration.
+     *
+     * @param int $contextId
+     * @return UserGroup|null
      */
     public function getFirstSubmitAsAuthorUserGroup(int $contextId): ?UserGroup
     {
-        return Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$contextId])
-            ->filterByRoleIds([Role::ROLE_ID_AUTHOR])
-            ->filterByPermitSelfRegistration(true)
-            ->limit(1)
-            ->getMany()
+        return UserGroup::query()
+            ->withContextIds([$contextId])
+            ->withRoleIds([Role::ROLE_ID_AUTHOR])
+            ->permitSelfRegistration(true)
             ->first();
     }
 
     /**
      * Load the XML file and move the settings to the DB
      *
-     * @param int $contextId
+     * @param int|null $contextId
      * @param string $filename
-     *
-     * @return bool true === success
+     * @return bool True on success otherwise false
      */
-    public function installSettings(?int $contextId, $filename)
+    public function installSettings(?int $contextId, string $filename): bool
     {
         $xmlParser = new PKPXMLParser();
         $tree = $xmlParser->parse($filename);
@@ -522,58 +527,60 @@ public function installSettings(?int $contextId, $filename)
             $roleId = hexdec($setting->getAttribute('roleId'));
             $nameKey = $setting->getAttribute('name');
             $abbrevKey = $setting->getAttribute('abbrev');
-            $permitSelfRegistration = $setting->getAttribute('permitSelfRegistration');
-            $permitMetadataEdit = $setting->getAttribute('permitMetadataEdit');
-            $masthead = $setting->getAttribute('masthead');
+            $permitSelfRegistration = $setting->getAttribute('permitSelfRegistration') === 'true';
+            $permitMetadataEdit = $setting->getAttribute('permitMetadataEdit') === 'true';
+            $masthead = $setting->getAttribute('masthead') === 'true';
 
             // If has manager role then permitMetadataEdit can't be overridden
-            if (in_array($roleId, [Role::ROLE_ID_MANAGER])) {
-                $permitMetadataEdit = $setting->getAttribute('permitMetadataEdit');
+            if (in_array($roleId, self::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES)) {
+                $permitMetadataEdit = $setting->getAttribute('permitMetadataEdit') === 'true';
             }
 
             $defaultStages = explode(',', (string) $setting->getAttribute('stages'));
 
-            // create a role associated with this user group
-            $userGroup = $this->newDataObject();
-            $userGroup->setRoleId($roleId);
-            $userGroup->setContextId($contextId);
-            $userGroup->setPermitSelfRegistration($permitSelfRegistration ?? false);
-            $userGroup->setPermitMetadataEdit($permitMetadataEdit ?? false);
-            $userGroup->setDefault(true);
-            $userGroup->setShowTitle(true);
-            $userGroup->setMasthead($masthead ?? false);
+            // Create a new UserGroup instance and set attributes
+            $userGroup = new UserGroup([
+                'roleId' => $roleId,
+                'contextId' => $contextId,
+                'permitSelfRegistration' => $permitSelfRegistration,
+                'permitMetadataEdit' => $permitMetadataEdit,
+                'isDefault' => true,
+                'showTitle' => true,
+                'masthead' => $masthead,
+            ]);
+
+            // Save the UserGroup instance to the database
+            $userGroup->save();
 
-            // insert the group into the DB
-            $userGroupId = $this->add($userGroup);
+            $userGroupId = $userGroup->userGroupId;
 
             // Install default groups for each stage
-            if (is_array($defaultStages)) { // test for groups with no stage assignments
-                foreach ($defaultStages as $stageId) {
-                    if (!empty($stageId) && $stageId <= WORKFLOW_STAGE_ID_PRODUCTION && $stageId >= WORKFLOW_STAGE_ID_SUBMISSION) {
-                        UserGroupStage::create([
-                            'contextId' => $contextId,
-                            'userGroupId' => $userGroupId,
-                            'stageId' => $stageId
-                        ]);
-                    }
+            foreach ($defaultStages as $stageId) {
+                $stageId = (int) trim($stageId);
+                if ($stageId >= WORKFLOW_STAGE_ID_SUBMISSION && $stageId <= WORKFLOW_STAGE_ID_PRODUCTION) {
+                    UserGroupStage::create([
+                        'context_id' => $contextId,
+                        'user_group_id' => $userGroupId,
+                        'stage_id' => $stageId,
+                    ]);
                 }
             }
 
-            // add the i18n keys to the settings table so that they
-            // can be used when a new locale is added/reloaded
-            $newUserGroup = $this->get($userGroupId);
-            $this->edit($newUserGroup, [
+            // Update the settings for nameLocaleKey and abbrevLocaleKey directly
+            $userGroup->fill([
                 'nameLocaleKey' => $nameKey,
-                'abbrevLocaleKey' => $abbrevKey
+                'abbrevLocaleKey' => $abbrevKey,
             ]);
 
-            // install the settings in the current locale for this context
+            $userGroup->save();
+    
+            // Install the settings in the current locale for this context
             foreach ($installedLocales as $locale) {
                 $this->installLocale($locale, $contextId);
             }
         }
 
-        self::forgetEditorialMastheadCache($contextId);
+        self::forgetEditorialCache($contextId);
         self::forgetEditorialHistoryCache($contextId);
 
         return true;
@@ -584,94 +591,109 @@ public function installSettings(?int $contextId, $filename)
      *
      * @param string $locale
      * @param ?int $contextId
+     * @return void
      */
-    public function installLocale($locale, ?int $contextId = null)
+    public function installLocale(string $locale, ?int $contextId = null): void
     {
-        $userGroupsCollector = $this->getCollector();
+        $userGroups = UserGroup::query();
 
-        if (isset($contextId)) {
-            $userGroupsCollector->filterByContextIds([$contextId]);
+        if ($contextId !== null) {
+            $userGroups->withContextIds([$contextId]);
         }
 
-        $userGroups = $userGroupsCollector->getMany();
+        $userGroups = $userGroups->get();
 
         foreach ($userGroups as $userGroup) {
-            $nameKey = $userGroup->getData('nameLocaleKey');
-            $userGroup->setData('name', __($nameKey, [], $locale), $locale);
-            $abbrevKey = $userGroup->getData('abbrevLocaleKey');
-            $userGroup->setData('abbrev', __($abbrevKey, [], $locale), $locale);
+            $nameKey = $userGroup->getSettings('nameLocaleKey') ?? null;
+            $abbrevKey = $userGroup->getSettings('abbrevLocaleKey') ?? null;
+
+            if ($nameKey) {
+                $userGroup->setData('name', [$locale => __($nameKey, [], $locale)]);
+            }
+
+            if ($abbrevKey) {
+                $userGroup->setData('abbrev', [$locale => __($abbrevKey, [], $locale)]);
+            }
 
-            $this->edit($userGroup, []);
+            $userGroup->save();
         }
     }
 
     /**
-     * Cache/get cached array of masthead user IDs grouped by masthead role IDs [user_group_id => [user_ids]]
+     * Cache/get cached array of masthead user IDs grouped by masthead role IDs
+     * Format: [user_group_id => [user_ids]]
      *
      * @param array $mastheadRoles Masthead roles, filtered by the given context ID, and sorted as they should appear on the Editorial Masthead and Editorial History page
-     *
+     * @param int $contextId
+     * @param UserUserGroupStatus $userUserGroupStatus
+     * @return array
      */
     public function getMastheadUserIdsByRoleIds(array $mastheadRoles, int $contextId, UserUserGroupStatus $userUserGroupStatus = UserUserGroupStatus::STATUS_ACTIVE): array
     {
-        $key = __METHOD__;
-        switch ($userUserGroupStatus) {
-            case UserUserGroupStatus::STATUS_ACTIVE:
-                $key .= 'EditorialMasthead';
-                break;
-            case UserUserGroupStatus::STATUS_ENDED:
-                $key .= 'EditorialHistory';
-                break;
-        }
-        $key .= $contextId . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME;
-        $expiration = DateInterval::createFromDateString(static::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME);
-        $allUsersIdsGroupedByUserGroupId = Cache::remember($key, $expiration, function () use ($mastheadRoles, $contextId, $userUserGroupStatus) {
-            $mastheadRolesIds = array_map(
-                function (UserGroup $item) use ($contextId) {
-                    if ($item->getContextId() == $contextId) {
-                        return $item->getId();
-                    }
-                },
-                $mastheadRoles
-            );
+        $statusSuffix = match ($userUserGroupStatus) {
+            UserUserGroupStatus::STATUS_ACTIVE => 'EditorialMasthead',
+            UserUserGroupStatus::STATUS_ENDED => 'EditorialHistory',
+            default => 'EditorialMasthead',
+        };
+
+        $cacheKey = __METHOD__ . $statusSuffix . $contextId . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME;
+        $expiration = DateInterval::createFromDateString(self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME);
+
+        return Cache::remember($cacheKey, $expiration, function () use ($mastheadRoles, $contextId, $userUserGroupStatus) {
+            // extract UserGroup IDs from mastheadRoles within the context
+            $mastheadRoleIds = array_map(fn (UserGroup $item) => $item->userGroupId, $mastheadRoles);
+
             // Query that gets all users that are or were active in the given masthead roles
             // and that have accepted to be displayed on the masthead for the roles.
             // Sort the results by role ID and user family name.
-            $usersCollector = Repo::user()->getCollector();
-            $usersQuery = $usersCollector
-                ->filterByContextIds([$contextId])
-                ->filterByUserGroupIds($mastheadRolesIds)
-                ->filterByUserUserGroupStatus($userUserGroupStatus)
-                ->filterByUserUserGroupMastheadStatus(UserUserGroupMastheadStatus::STATUS_ON)
-                ->orderBy($usersCollector::ORDERBY_FAMILYNAME, $usersCollector::ORDER_DIR_ASC, [Locale::getLocale(), Application::get()->getRequest()->getSite()->getPrimaryLocale()])
-                ->orderByUserGroupIds($mastheadRolesIds)
-                ->getQueryBuilder()
-                ->get();
-
-            // Get unique user IDs grouped by user group ID
-            $userIdsByUserGroupId = $usersQuery->mapToGroups(function (stdClass $item, int $key) {
-                return [$item->user_group_id => $item->user_id];
-            })->map(function ($item) {
-                return collect($item)->unique();
-            });
-            return $userIdsByUserGroupId->toArray();
+            $users = UserUserGroup::query()
+                ->withContextId($contextId)
+                ->withUserGroupIds($mastheadRoleIds)
+                ->withUserUserGroupStatus($userUserGroupStatus->value)
+                ->withUserUserGroupMastheadStatus(UserUserGroupMastheadStatus::STATUS_ON->value)
+                ->orderBy('user_groups.role_id', 'asc')
+                ->join('user_groups', 'user_user_groups.user_group_id', '=', 'user_groups.user_group_id')
+                ->join('users', 'user_user_groups.user_id', '=', 'users.user_id')
+                ->orderBy('users.family_name', 'asc')
+                ->get(['user_groups.user_group_id', 'users.user_id']);
+
+            // group unique user ids by UserGroup id
+            $userIdsByUserGroupId = $users->groupBy('user_group_id')->map(function ($group) {
+                return $group->pluck('user_id')->unique()->toArray();
+            })->toArray();
+
+            return $userIdsByUserGroupId;
         });
-        return $allUsersIdsGroupedByUserGroupId;
     }
 
     /**
-     * Clear editorial masthead cache
+     * Clear editorial masthead cache for a given context
+     *
+     * @param int $contextId
+     * @return void
      */
-    public static function forgetEditorialMastheadCache(int $contextId)
+    public static function forgetEditorialCache(int $contextId): void
     {
-        Cache::forget('PKP\userGroup\Repository::getMastheadUserIdsByRoleIdsEditorialMasthead' . $contextId . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME);
+        $cacheKeyPrefix = 'PKP\userGroup\Repository::getMastheadUserIdsByRoleIds';
+        $cacheKeys = [
+            "{$cacheKeyPrefix}EditorialMasthead{$contextId}" . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME,
+            "{$cacheKeyPrefix}EditorialHistory{$contextId}" . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME,
+        ];
+
+        foreach ($cacheKeys as $key) {
+            Cache::forget($key);
+        }
     }
 
     /**
-     * Clear editorial history cache
+     * Clear editorial history cache for a given context.
+     *
+     * @param int $contextId
+     * @return void
      */
-    public static function forgetEditorialHistoryCache(int $contextId)
+    public static function forgetEditorialHistoryCache(int $contextId): void
     {
-        Cache::forget('PKP\userGroup\Repository::getMastheadUserIdsByRoleIdsEditorialHistory' . $contextId . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME);
+        $cacheKey = "PKP\userGroup\Repository::getMastheadUserIdsByRoleIdsEditorialHistory{$contextId}" . self::MAX_EDITORIAL_MASTHEAD_CACHE_LIFETIME;
+        Cache::forget($cacheKey);
     }
-
 }
diff --git a/classes/userGroup/UserGroup.php b/classes/userGroup/UserGroup.php
index 404180d2c98..4000a80cb5a 100644
--- a/classes/userGroup/UserGroup.php
+++ b/classes/userGroup/UserGroup.php
@@ -3,263 +3,488 @@
 /**
  * @file classes/userGroup/UserGroup.php
  *
- * Copyright (c) 2014-2021 Simon Fraser University
- * Copyright (c) 2000-2021 John Willinsky
+ * Copyright (c) 2014-2014 Simon Fraser University
+ * Copyright (c) 2000-2024 John Willinsky
  * Distributed under the GNU GPL v3. For full terms see the file docs/COPYING.
  *
  * @class \PKP\userGroup\UserGroup
  *
- * @see DAO
- *
- * @brief UserGroup metadata class.
+ * @brief Eloquent Model for UserGroup
  */
 
-namespace PKP\userGroup;
+ namespace PKP\userGroup;
+
+ use Illuminate\Database\Eloquent\Builder as EloquentBuilder;
+ use Illuminate\Database\Eloquent\Model;
+ use Illuminate\Database\Eloquent\Relations\HasMany;
+ use PKP\core\traits\ModelWithSettings;
+ use PKP\stageAssignment\StageAssignment;
+ use PKP\userGroup\relationships\UserUserGroup;
+ use PKP\userGroup\relationships\UserGroupStage;
+ use PKP\facades\Locale;
+ use PKP\plugins\Hook;
+ use PKP\facades\Repo;
+ use PKP\services\PKPSchemaService;
+ use PKP\core\PKPApplication;
+ use APP\core\Application;
 
-use PKP\core\PKPApplication;
 
-class UserGroup extends \PKP\core\DataObject
+class UserGroup extends Model
 {
+    
+    use ModelWithSettings;
+
+
+    /**
+     * The table associated with the model.
+     *
+     * @var string
+     */
+    protected $table = 'user_groups';
+
+    /**
+     * The primary key associated with the table.
+     *
+     * @var string
+     */
+    protected $primaryKey = 'user_group_id';
+
     /**
-     * Get the role ID
+     * Indicates if the model should be timestamped.
      *
-     * @return int ROLE_ID_...
+     * @var bool
      */
-    public function getRoleId()
+    public $timestamps = false;
+
+    /**
+     * The attributes that are mass assignable.
+     *
+     * @var array
+     */
+    protected $fillable = [
+        'contextId',
+        'roleId',
+        'isDefault',
+        'showTitle',
+        'permitSelfRegistration',
+        'permitMetadataEdit',
+        'masthead',
+    ];
+
+    /**
+     * The attributes that should be cast.
+     *
+     * @return array<string, string>
+     */
+    protected function casts(): array
     {
-        return $this->getData('roleId');
+        return [
+            'contextId' => 'integer',
+            'roleId' => 'integer',
+            'isDefault' => 'boolean',
+            'showTitle' => 'boolean',
+            'permitSelfRegistration' => 'boolean',
+            'permitMetadataEdit' => 'boolean',
+            'masthead' => 'boolean',
+        ];
     }
 
     /**
-     * Set the role ID
-     *
-     * @param int $roleId ROLE_ID_...
+     * Get the settings table name
+     */
+    public function getSettingsTable(): string
+    {
+        return 'user_group_settings';
+    }
+
+    /**
+     * Get the schema name for the model
+     */
+    public static function getSchemaName(): ?string
+    {
+        return PKPSchemaService::SCHEMA_USER_GROUP;
+    }
+
+    /**
+     * Define multilingual properties
      */
-    public function setRoleId($roleId)
+    public function getMultilingualProps(): array
     {
-        $this->setData('roleId', $roleId);
+        return [
+            'name',
+            'namePlural',
+            'abbrev',
+        ];
     }
 
     /**
-     * Get the role path
+     * Get assigned stage IDs
      *
-     * @return string Role path
+     * @return \Illuminate\Support\Collection
      */
-    public function getPath()
+    public function getAssignedStageIds()
     {
-        return $this->getData('path');
+        return $this->userGroupStages()->pluck('stage_id');
     }
 
     /**
-     * Set the role path
-     * $param $path string
+     * Define the relationship to UserUserGroups
      */
-    public function setPath($path)
+    public function userUserGroups(): HasMany
     {
-        $this->setData('path', $path);
+        return $this->hasMany(UserUserGroup::class, 'user_group_id', 'user_group_id');
     }
 
     /**
-     * Get the context ID
+     * Define the relationship to UserGroupStages
      */
-    public function getContextId(): ?int
+    public function userGroupStages(): HasMany
+    {
+        return $this->hasMany(UserGroupStage::class, 'user_group_id', 'user_group_id');
+    }
+
+    protected function scopeWithContextIds(EloquentBuilder $builder, $contextIds): EloquentBuilder
     {
-        return $this->getData('contextId');
+        if (empty($contextIds)) {
+            return $builder;
+        }
+    
+        if (!is_array($contextIds)) {
+            $contextIds = [$contextIds];
+        }
+    
+        return $builder->whereIn('context_id', $contextIds);
     }
 
     /**
-     * Set the context ID
+     * Scope a query to filter by user group IDs.
      */
-    public function setContextId(?int $contextId): void
+    protected function scopeWithUserGroupIds(EloquentBuilder $builder, $userGroupIds): EloquentBuilder
     {
-        $this->setData('contextId', $contextId);
+        if (!is_array($userGroupIds)) {
+            $userGroupIds = [$userGroupIds];
+        }
+    
+        return $builder->whereIn('user_group_id', $userGroupIds);
     }
 
     /**
-     * Get the default flag
-     *
-     * @return bool
+     * Scope a query to filter by role IDs.
      */
-    public function getDefault()
+    protected function scopeWithRoleIds(EloquentBuilder $builder, $roleIds): EloquentBuilder
     {
-        return $this->getData('isDefault');
+        if (!is_array($roleIds)) {
+            $roleIds = [$roleIds];
+        }
+    
+        return $builder->whereIn('role_id', $roleIds);
     }
 
     /**
-     * Set the default flag
-     *
-     * @param bool $isDefault
+     * Scope a query to exclude certain role IDs.
      */
-    public function setDefault($isDefault)
+    protected function scopeExcludeRoles(EloquentBuilder $builder, array $excludeRoles): EloquentBuilder
     {
-        $this->setData('isDefault', $isDefault);
+        return $builder->whereNotIn('role_id', $excludeRoles);
     }
 
     /**
-     * Get the "show title" flag (whether or not the title of the role
-     * should be included in the list of submission contributor names)
-     *
-     * @return bool
+     * Scope a query to filter by stage IDs.
      */
-    public function getShowTitle()
+    protected function scopeWithStageIds(EloquentBuilder $builder, $stageIds): EloquentBuilder
     {
-        return $this->getData('showTitle');
+        if (!is_array($stageIds)) {
+            $stageIds = [$stageIds];
+        }
+        return $builder->whereHas('userGroupStages', function (EloquentBuilder $q) use ($stageIds) {
+            $q->whereIn('stage_id', $stageIds);
+        });
     }
 
     /**
-     * Set the "show title" flag
-     *
-     * @param bool $showTitle
+     * Scope a query to exclude role ids.
      */
-    public function setShowTitle($showTitle)
+    protected function scopeExcludeRoleIds(EloquentBuilder $builder, $roleIds): EloquentBuilder
     {
-        $this->setData('showTitle', $showTitle);
+        if (!is_array($roleIds)) {
+            $roleIds = [$roleIds];
+        }
+        return $builder->whereNotIn('role_id', $roleIds);
     }
 
     /**
-     * Get the "permit self-registration" flag (whether or not users may
-     * self-register for this role, i.e. in the case of external
-     * reviewers, or whether it should be prohibited, in the case of
-     * internal reviewers).
-     *
-     * @return bool True IFF user self-registration is permitted
+     * Scope a query to filter by is_default.
      */
-    public function getPermitSelfRegistration()
+    protected function scopeIsDefault(EloquentBuilder $builder, bool $isDefault): EloquentBuilder
     {
-        return $this->getData('permitSelfRegistration');
+        return $builder->where('is_default', $isDefault);
     }
 
     /**
-     * Set the "permit self-registration" flag
+     * Scope a query to filter by show_title.
      */
-    public function setPermitSelfRegistration(bool $permitSelfRegistration)
+    protected function scopeShowTitle(EloquentBuilder $builder, bool $showTitle): EloquentBuilder
     {
-        $this->setData('permitSelfRegistration', $permitSelfRegistration);
+        return $builder->where('show_title', $showTitle);
     }
 
     /**
-     * Get the recommendOnly option (whether or not the manager or the sub-editor role
-     * can only recommend or also make decisions in the submission review)
-     *
-     * @return bool
+     * Scope a query to filter by permit_self_registration.
      */
-    public function getRecommendOnly()
+    protected function scopePermitSelfRegistration(EloquentBuilder $builder, bool $permitSelfRegistration): EloquentBuilder
     {
-        return $this->getData('recommendOnly');
+        return $builder->where('permit_self_registration', $permitSelfRegistration);
     }
 
     /**
-     * Set the recommendOnly option (whether or not the manager or the sub-editor role
-     * can only recommend or also make decisions in the submission review)
-     *
-     * @param bool $recommendOnly
+     * Scope a query to filter by permit_metadata_edit.
      */
-    public function setRecommendOnly($recommendOnly)
+    protected function scopePermitMetadataEdit(EloquentBuilder $builder, bool $permitMetadataEdit): EloquentBuilder
     {
-        $this->setData('recommendOnly', $recommendOnly);
+        return $builder->where('permit_metadata_edit', $permitMetadataEdit);
     }
 
     /**
-     * Get the localized role name
-     *
-     * @return string
+     * Scope a query to filter by masthead.
      */
-    public function getLocalizedName()
+    protected function scopeMasthead(EloquentBuilder $builder, bool $masthead): EloquentBuilder
     {
-        return $this->getLocalizedData('name');
+        return $builder->where('masthead', $masthead);
     }
 
     /**
-     * Get localized user group name, or array of localized names if $locale is null
-     *
-     * @param string|null $locale
-     *
-     * @return string|array|null localized name or array of localized names or null
+     * Scope a query to filter by user IDs.
+     */
+    protected function scopeWithUserIds(EloquentBuilder $builder, array $userIds): EloquentBuilder
+    {
+        return $builder->whereHas('userUserGroups', function (EloquentBuilder $q) use ($userIds) {
+            $q->whereIn('user_id', $userIds);
+        });
+    }
+
+    /**
+     * Scope a query to filter by recommendOnly setting.
+     */
+    protected function scopeIsRecommendOnly(EloquentBuilder $builder, bool $isRecommendOnly): EloquentBuilder
+    {
+        return $builder->where('recommendOnly', $isRecommendOnly);
+    }
+
+    /**
+     * Scope a query to filter by UserUserGroupStatus.
+     */
+    protected function scopeWithUserUserGroupStatus(EloquentBuilder $builder, string $status): EloquentBuilder
+    {
+        $currentDateTime = now();
+
+        if ($status === 'active') {
+            $builder->whereHas('userUserGroups', function (EloquentBuilder $q) use ($currentDateTime) {
+                $q->where(function (EloquentBuilder $q) use ($currentDateTime) {
+                    $q->where('date_start', '<=', $currentDateTime)
+                        ->orWhereNull('date_start');
+                })->where(function (EloquentBuilder $q) use ($currentDateTime) {
+                    $q->where('date_end', '>', $currentDateTime)
+                        ->orWhereNull('date_end');
+                });
+            });
+        } elseif ($status === 'ended') {
+            $builder->whereHas('userUserGroups', function (EloquentBuilder $q) use ($currentDateTime) {
+                $q->whereNotNull('date_end')
+                    ->where('date_end', '<=', $currentDateTime);
+            });
+        }
+        // Implement other statuses if needed
+        return $builder;
+    }
+
+    /**
+     * Scope a query to order by role ID.
+     */
+    protected function scopeOrderByRoleId(EloquentBuilder $builder): EloquentBuilder
+    {
+        return $builder->orderBy('role_id', 'asc');
+    }
+
+    /**
+     * Scope a query to order by user group ID.
+     */
+    protected function scopeOrderById(EloquentBuilder $builder): EloquentBuilder
+    {
+        return $builder->orderBy('user_group_id', 'asc');
+    }
+
+    /**
+     * Scope a query to include active user count.
      */
-    public function getName($locale)
+    protected function scopeWithActiveUserCount(EloquentBuilder $builder, ?int $contextId = null): EloquentBuilder
     {
-        return $this->getData('name', $locale);
+        $currentDateTime = now();
+
+        $builder->select('user_groups.user_group_id')
+            ->selectRaw('COUNT(user_user_groups.user_id) AS count')
+            ->join('user_user_groups', 'user_user_groups.user_group_id', '=', 'user_groups.user_group_id')
+            ->join('users', 'users.user_id', '=', 'user_user_groups.user_id')
+            ->where('users.disabled', 0)
+            ->where(function (EloquentBuilder $q) use ($currentDateTime) {
+                $q->where('user_user_groups.date_start', '<=', $currentDateTime)
+                    ->orWhereNull('user_user_groups.date_start');
+            })
+            ->where(function (EloquentBuilder $q) use ($currentDateTime) {
+                $q->where('user_user_groups.date_end', '>', $currentDateTime)
+                    ->orWhereNull('user_user_groups.date_end');
+            })
+            ->groupBy('user_groups.user_group_id');
+
+        if ($contextId !== null) {
+            $builder->where('user_groups.context_id', $contextId);
+        }
+
+        return $builder;
     }
 
     /**
-     * Set user group name
+     * Ensure casts are string values.
      *
-     * @param string $name
-     * @param string $locale
+     * @param array $casts
+     * @return array
      */
-    public function setName($name, $locale)
+    protected function ensureCastsAreStringValues($casts): array
     {
-        $this->setData('name', $name, $locale);
+        return array_map(fn($cast) => (string) $cast, $casts);
     }
 
+
     /**
-     * Get the localized abbreviation
+     * Scope a query to filter by publication IDs.
      *
-     * @return string
+     * @param EloquentBuilder $builder
+     * @param array<int> $publicationIds Array of publication IDs to filter by.
+     * @return EloquentBuilder
      */
-    public function getLocalizedAbbrev()
+    protected function scopeWithPublicationIds(EloquentBuilder $builder, array $publicationIds): EloquentBuilder
     {
-        return $this->getLocalizedData('abbrev');
+        return $builder->whereHas('userUserGroups', function (EloquentBuilder $q) use ($publicationIds) {
+            $q->whereIn('publication_id', $publicationIds);
+        });
     }
 
     /**
-     * Get localized user group abbreviation, or array of localized abbreviations if $locale is null
+     * Set the name attribute.
      *
-     * @param string|null $locale
+     * @param mixed $value
+     * @return void
+     */
+    public function setNameAttribute($value): void
+    {
+        if (is_string($value)) {
+            $value = $this->localizeNonLocalizedData($value);
+        }
+        $this->setData('name', $value);
+    }
+
+    /**
+     * Set the abbrev attribute.
      *
-     * @return string|array|null localized abbreviation or array of localized abbreviations or null
+     * @param mixed $value
+     * @return void
      */
-    public function getAbbrev($locale)
+    public function setAbbrevAttribute($value): void
     {
-        return $this->getData('abbrev', $locale);
+        if (is_string($value)) {
+            $value = $this->localizeNonLocalizedData($value);
+        }
+        $this->setData('abbrev', $value);
     }
 
     /**
-     * Set user group abbreviation
+     * Localize non-localized data.
      *
-     * @param string $abbrev
-     * @param string $locale
+     * @param string $value
+     * @return array
      */
-    public function setAbbrev($abbrev, $locale)
+    protected function localizeNonLocalizedData(string $value): array
     {
-        $this->setData('abbrev', $abbrev, $locale);
+        return [Locale::getLocale() => $value];
     }
 
     /**
-     * Getter for permitMetadataEdit attribute.
+     * Find a UserGroup by ID and optional context ID.
      *
-     * @return bool
+     * @param int $id
+     * @param int|null $contextId
+     * @return self|null
      */
-    public function getPermitMetadataEdit()
+    public static function findById(int $id, ?int $contextId = null): ?self
     {
-        return $this->getData('permitMetadataEdit');
+        $query = self::where('user_group_id', $id);
+
+        if ($contextId !== null) {
+            $query->withContextIds([$contextId]);
+        }
+
+        return $query->first();
     }
 
     /**
-     * Setter for permitMetadataEdit attribute.
+     * Save the model to the database.
+     *
+     * @param array $options
+     * @return bool
      */
-    public function setPermitMetadataEdit(bool $permitMetadataEdit)
+    public function save(array $options = [])
     {
-        $this->setData('permitMetadataEdit', $permitMetadataEdit);
+        $isNew = !$this->exists;
+
+        $saved = parent::save($options);
+
+        // Reload the model to ensure all relationships and settings are loaded
+        $this->refresh();
+
+        if ($isNew) {
+            // This is a new record
+            Hook::call('UserGroup::add', [$this]);
+        } else {
+            // This is an update
+            Hook::call('UserGroup::edit', [$this]);
+        }
+
+        // Clear editorial masthead cache if the role is on the masthead
+        if ($this->masthead) {
+            Repo::userGroup()->forgetEditorialCache($this->contextId);
+            Repo::userGroup()->forgetEditorialHistoryCache($this->contextId);
+        }
+
+        return $saved;
     }
 
     /**
-     * Get the masthead flag
+     * Booted method to handle model events.
+     *
+     * @return void
      */
-    public function getMasthead(): bool
+    protected static function booted()
     {
-        return $this->getData('masthead');
+        static::deleting(function ($userGroup) {
+            // Equivalent to 'UserGroup::delete::before' hook
+            Hook::call('UserGroup::delete::before', [$userGroup]);
+
+            if ($userGroup->masthead) {
+                Repo::userGroup()->forgetEditorialCache($userGroup->contextId);
+                Repo::userGroup()->forgetEditorialHistoryCache($userGroup->contextId);
+            }
+        });
+
+        static::deleted(function ($userGroup) {
+            Hook::call('UserGroup::delete', [$userGroup]);
+        });
     }
 
     /**
-     * Set the masthead flag
+     * Define the relationship to StageAssignments.
      */
-    public function setMasthead(bool $masthead)
+    public function stageAssignments(): HasMany
     {
-        $this->setData('masthead', $masthead);
+        return $this->hasMany(StageAssignment::class, 'user_group_id', 'user_group_id');
     }
-}
 
-if (!PKP_STRICT_MODE) {
-    class_alias('\PKP\userGroup\UserGroup', '\UserGroup');
 }
diff --git a/classes/userGroup/maps/Schema.php b/classes/userGroup/maps/Schema.php
index 74be1816d14..10bc0e00993 100644
--- a/classes/userGroup/maps/Schema.php
+++ b/classes/userGroup/maps/Schema.php
@@ -84,7 +84,7 @@ protected function mapByProperties(array $props, UserGroup $item): array
         foreach ($props as $prop) {
             switch ($prop) {
                 default:
-                    $output[$prop] = $item->getData($prop);
+                    $output[$prop] = $item->getAttribute($prop);
                     break;
             }
         }
diff --git a/classes/userGroup/relationships/UserGroupStage.php b/classes/userGroup/relationships/UserGroupStage.php
index d9f27afc4b0..8f6cf802195 100644
--- a/classes/userGroup/relationships/UserGroupStage.php
+++ b/classes/userGroup/relationships/UserGroupStage.php
@@ -14,10 +14,11 @@
 
 namespace PKP\userGroup\relationships;
 
-use APP\facades\Repo;
 use Illuminate\Database\Eloquent\Builder;
-use Illuminate\Database\Eloquent\Casts\Attribute;
 use Eloquence\Behaviours\HasCamelCasing;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use PKP\userGroup\UserGroup;
+
 
 class UserGroupStage extends \Illuminate\Database\Eloquent\Model
 {
@@ -35,12 +36,10 @@ class UserGroupStage extends \Illuminate\Database\Eloquent\Model
      */
     protected $table = 'user_group_stage';
 
-    public function userGroup(): Attribute
+
+    public function userGroup(): BelongsTo
     {
-        return Attribute::make(
-            get: fn ($value, $attributes) => Repo::userGroup()->get($attributes['user_group_id']),
-            set: fn ($value) => $value->getId()
-        );
+        return $this->belongsTo(UserGroup::class, 'user_group_id', 'user_group_id');
     }
 
     public function scopeWithStageId(Builder $query, int $stageId): Builder
@@ -48,6 +47,11 @@ public function scopeWithStageId(Builder $query, int $stageId): Builder
         return $query->where('stage_id', $stageId);
     }
 
+    public function scopeWithStageIds(Builder $query, array $stageIds): Builder
+    {
+        return $query->whereIn('stage_id', $stageIds);
+    }
+
     public function scopeWithUserGroupId(Builder $query, int $userGroupId): Builder
     {
         return $query->where('user_group_id', $userGroupId);
diff --git a/classes/userGroup/relationships/UserUserGroup.php b/classes/userGroup/relationships/UserUserGroup.php
index b930efbe271..e54e2f7f11a 100644
--- a/classes/userGroup/relationships/UserUserGroup.php
+++ b/classes/userGroup/relationships/UserUserGroup.php
@@ -17,8 +17,10 @@
 use APP\facades\Repo;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Casts\Attribute;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Eloquence\Behaviours\HasCamelCasing;
 use PKP\core\Core;
+use PKP\userGroup\UserGroup;
 
 class UserUserGroup extends \Illuminate\Database\Eloquent\Model
 {
@@ -37,12 +39,12 @@ public function user(): Attribute
         );
     }
 
-    public function userGroup(): Attribute
+    /**
+     * Define the relationship to UserGroup
+     */
+    public function userGroup(): BelongsTo
     {
-        return Attribute::make(
-            get: fn ($value, $attributes) => Repo::userGroup()->get($attributes['user_group_id']),
-            set: fn ($value) => $value->getId()
-        );
+        return $this->belongsTo(UserGroup::class, 'user_group_id', 'user_group_id');
     }
 
     public function scopeWithUserId(Builder $query, int $userId): Builder
diff --git a/controllers/api/file/PKPManageFileApiHandler.php b/controllers/api/file/PKPManageFileApiHandler.php
index 150b24fab23..1e046253b35 100644
--- a/controllers/api/file/PKPManageFileApiHandler.php
+++ b/controllers/api/file/PKPManageFileApiHandler.php
@@ -223,7 +223,7 @@ public function saveMetadata($args, $request)
                 ->get();
 
             $authorUserIds = $submitterAssignments
-                ->pluck('userId')
+                ->pluck('user_id')
                 ->all();
 
             // Update the notifications
diff --git a/controllers/grid/queries/form/QueryForm.php b/controllers/grid/queries/form/QueryForm.php
index 3f623f6db32..30b49e412f8 100644
--- a/controllers/grid/queries/form/QueryForm.php
+++ b/controllers/grid/queries/form/QueryForm.php
@@ -36,6 +36,8 @@
 use PKP\security\Role;
 use PKP\stageAssignment\StageAssignment;
 use PKP\submission\reviewAssignment\ReviewAssignment;
+use PKP\userGroup\UserGroup;
+use PKP\userGroup\relationships\UserUserGroup;
 
 class QueryForm extends Form
 {
@@ -233,6 +235,28 @@ public function initData()
         return parent::initData();
     }
 
+    /**
+     * Get the assigned roles for a user in a submission and stage.
+     */
+    private function getAssignedRoles($submissionId, $stageId, $userId)
+    {
+        $assignedRoles = [];
+        $usersAssignments = StageAssignment::with(['userGroup'])
+            ->withSubmissionIds([$submissionId])
+            ->withStageIds([$stageId])
+            ->withUserId($userId)
+            ->get();
+
+        foreach ($usersAssignments as $usersAssignment) {
+            $userGroup = $usersAssignment->userGroup;
+            if ($userGroup) {
+                $assignedRoles[] = $userGroup->roleId;
+            }
+        }
+
+        return $assignedRoles;
+    }
+
     /**
      * Fetch the form.
      *
@@ -288,61 +312,54 @@ public function fetch($request, $template = null, $display = false, $actionArgs
         $templateMgr->assign('templates', $templateKeySubjectPairs);
 
         // Get currently selected participants in the query
-
-        $assignedParticipants = $query->id ? QueryParticipant::withQueryId($query->id)->pluck('user_id')->all() : [];
+        $assignedParticipants = $query->id
+            ? QueryParticipant::withQueryId($query->id)->get()->map(fn($qp) => $qp->userId)->all()
+            : [];
 
         // Always include current user, even if not with a stage assignment
-        $includeUsers[] = $user->getId();
+        $includeUsers = [$user->getId()];
         $excludeUsers = null;
 
-        // When in review stage, include/exclude users depending on the current users role
+        // When in review stage, include/exclude users depending on the current user's role
         $reviewAssignments = [];
-        // Get current users roles
-        $assignedRoles = (function () use ($query, $user) {
-            $assignedRoles = [];
-            // Replaces StageAssignmentDAO::getBySubmissionAndStageId
-            $usersAssignments = StageAssignment::withSubmissionIds([$query->assocId])
-                ->withStageIds([$query->stageId])
-                ->withUserId($user->getId())
-                ->get();
-
-            foreach ($usersAssignments as $usersAssignment) {
-                $userGroup = Repo::userGroup()->get($usersAssignment->userGroupId);
-                $assignedRoles[] = $userGroup->getRoleId();
-            }
-            return $assignedRoles;
-        })();
+        // Get current user's roles
+        $assignedRoles = $this->getAssignedRoles($query->assocId, $query->stageId, $user->getId());
 
         if ($query->stageId == WORKFLOW_STAGE_ID_EXTERNAL_REVIEW || $query->stageId == WORKFLOW_STAGE_ID_INTERNAL_REVIEW) {
             // Get all review assignments for current submission
             $reviewAssignments = Repo::reviewAssignment()->getCollector()->filterBySubmissionIds([$submission->getId()])->getMany();
 
             // if current user is editor/journal manager/site admin and not have author role , add all reviewers
-            if (array_intersect($assignedRoles, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR]) || (empty($assignedRoles) && ($user->hasRole([Role::ROLE_ID_MANAGER], $context->getId()) || $user->hasRole([Role::ROLE_ID_SITE_ADMIN], PKPApplication::SITE_CONTEXT_ID)))) {
+            if (
+                array_intersect($assignedRoles, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR]) ||
+                (empty($assignedRoles) && ($user->hasRole([Role::ROLE_ID_MANAGER], $context->getId()) || $user->hasRole([Role::ROLE_ID_SITE_ADMIN], PKPApplication::SITE_CONTEXT_ID)))
+            ) {
                 foreach ($reviewAssignments as $reviewAssignment) {
                     $includeUsers[] = $reviewAssignment->getReviewerId();
                 }
             }
 
-            // if current user is an anonymous reviewer, filter out authors
+            // if current user is an anonymous reviewer, exclude authors
             foreach ($reviewAssignments as $reviewAssignment) {
                 if ($reviewAssignment->getReviewerId() == $user->getId()) {
                     if ($reviewAssignment->getReviewMethod() != ReviewAssignment::SUBMISSION_REVIEW_METHOD_OPEN) {
-                        // Replaces StageAssignmentDAO::getBySubmissionAndRoleId
                         $excludeUsers = StageAssignment::withSubmissionIds([$query->assocId])
                             ->withRoleIds([Role::ROLE_ID_AUTHOR])
-                            ->withUserId($user->getId())
                             ->get()
-                            ->pluck('userId')
+                            ->map(fn($assignment) => $assignment->userId)
                             ->all();
                     }
                 }
             }
 
-            // if current user is author, add open reviewers who have accepted the request
+            // If current user is author, include open reviewers who have accepted the request
             if (array_intersect([Role::ROLE_ID_AUTHOR], $assignedRoles)) {
                 foreach ($reviewAssignments as $reviewAssignment) {
-                    if ($reviewAssignment->getReviewMethod() == ReviewAssignment::SUBMISSION_REVIEW_METHOD_OPEN && $reviewAssignment->getDateConfirmed() && !$reviewAssignment->getDeclined()) {
+                    if (
+                        $reviewAssignment->getReviewMethod() == ReviewAssignment::SUBMISSION_REVIEW_METHOD_OPEN &&
+                        $reviewAssignment->getDateConfirmed() &&
+                        !$reviewAssignment->getDeclined()
+                    ) {
                         $includeUsers[] = $reviewAssignment->getReviewerId();
                     }
                 }
@@ -361,33 +378,38 @@ public function fetch($request, $template = null, $display = false, $actionArgs
         $usersIterator = $usersIterator->merge($includedUsersIterator);
 
         $allParticipants = [];
-        foreach ($usersIterator as $user) {
-            $allUserGroups = Repo::userGroup()->userUserGroups($user->getId(), $context->getId());
-
+        foreach ($usersIterator as $participantUser) {
+            // fetch user groups where the user is assigned in the current context
+            $allUserGroups = UserGroup::query()
+            ->withContextIds($context->getId())
+            ->whereHas('userUserGroups', function ($query) use ($participantUser) {
+                $query->withUserId($participantUser->getId())
+                      ->withActive();
+            })
+            ->get();
+    
             $userRoles = [];
-            // Replaces StageAssignmentDAO::getBySubmissionAndStageId
-            $userAssignments = StageAssignment::withSubmissionIds([$query->assocId])
-                ->withStageIds([$query->stageId])
-                ->withUserId($user->getId())
-                ->get();
+            // get participant's assigned roles
+            $participantAssignedRoles = $this->getAssignedRoles($query->assocId, $query->stageId, $participantUser->getId());
 
-            foreach ($userAssignments as $userAssignment) {
+            foreach ($participantAssignedRoles as $roleId) {
                 foreach ($allUserGroups as $userGroup) {
-                    if ($userGroup->getId() == $userAssignment->userGroupId) {
-                        $userRoles[] = $userGroup->getLocalizedName();
+                    if ($userGroup->roleId == $roleId) {
+                        $userRoles[] = $userGroup->getLocalizedData('name');
                     }
                 }
             }
+            // include reviewer roles if applicable
             foreach ($reviewAssignments as $assignment) {
-                if ($assignment->getReviewerId() == $user->getId()) {
+                if ($assignment->getReviewerId() == $participantUser->getId()) {
                     $userRoles[] = __('user.role.reviewer') . ' (' . __($assignment->getReviewMethodKey()) . ')';
                 }
             }
             if (!count($userRoles)) {
                 $userRoles[] = __('submission.status.unassigned');
             }
-            $allParticipants[$user->getId()] = __('submission.query.participantTitle', [
-                'fullName' => $user->getFullName(),
+            $allParticipants[$participantUser->getId()] = __('submission.query.participantTitle', [
+                'fullName' => $participantUser->getFullName(),
                 'userGroup' => join(__('common.commaListSeparator'), $userRoles),
             ]);
         }
@@ -448,18 +470,7 @@ public function validate($callHooks = true)
             $participantsToConsider = $blindReviewerCount = 0;
             foreach ($newParticipantIds as $participantId) {
                 // get participant roles in this workflow stage
-                $assignedRoles = [];
-                // Replaces StageAssignmentDAO::getBySubmissionAndStageId
-                $usersAssignments = StageAssignment::withSubmissionIds([$submissionId])
-                    ->withStageIds([$stageId])
-                    ->withUserId($participantId)
-                    ->get();
-
-                foreach ($usersAssignments as $usersAssignment) {
-                    $userGroup = Repo::userGroup()->get($usersAssignment->userGroupId);
-                    $assignedRoles[] = $userGroup->getRoleId();
-                }
-
+                $assignedRoles = $this->getAssignedRoles($submissionId, $stageId, $participantId);
                 if ($stageId == WORKFLOW_STAGE_ID_EXTERNAL_REVIEW || $stageId == WORKFLOW_STAGE_ID_INTERNAL_REVIEW) {
                     // validate the anonymity
                     // get participant review assignments
diff --git a/controllers/grid/settings/category/form/CategoryForm.php b/controllers/grid/settings/category/form/CategoryForm.php
index cc4317b860d..2bd6bd23d23 100644
--- a/controllers/grid/settings/category/form/CategoryForm.php
+++ b/controllers/grid/settings/category/form/CategoryForm.php
@@ -260,18 +260,17 @@ public function fetch($request, $template = null, $display = false)
         // Sort options.
         $templateMgr->assign('sortOptions', Repo::submission()->getSortSelectOptions());
 
-        $assignableUserGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$request->getContext()->getId()])
-            ->filterByRoleIds($this->assignableRoles)
-            ->filterByStageIds([WORKFLOW_STAGE_ID_SUBMISSION])
-            ->getMany()
+        $assignableUserGroups = UserGroup::query()
+            ->withContextIds([$request->getContext()->getId()])
+            ->withRoleIds($this->assignableRoles)
+            ->withStageIds([WORKFLOW_STAGE_ID_SUBMISSION])
+            ->get()
             ->map(function (UserGroup $userGroup) use ($request) {
                 return [
                     'userGroup' => $userGroup,
                     'users' => Repo::user()
                         ->getCollector()
-                        ->filterByUserGroupIds([$userGroup->getId()])
+                        ->filterByUserGroupIds([$userGroup->id])
                         ->filterByContextIds([$request->getContext()->getId()])
                         ->getMany()
                         ->mapWithKeys(fn ($user, $key) => [$user->getId() => $user->getFullName()])
diff --git a/controllers/grid/settings/roles/UserGroupGridCellProvider.php b/controllers/grid/settings/roles/UserGroupGridCellProvider.php
index 3282a6e16fd..cb198d62a56 100644
--- a/controllers/grid/settings/roles/UserGroupGridCellProvider.php
+++ b/controllers/grid/settings/roles/UserGroupGridCellProvider.php
@@ -45,26 +45,29 @@ public function getTemplateVarsFromRowColumn($row, $column)
         $workflowStages = Application::getApplicationStages();
         $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
 
-        $assignedStages = Repo::userGroup()->getAssignedStagesByUserGroupId($userGroup->getContextId(), $userGroup->getId())->toArray();
+        $assignedStages = Repo::userGroup()->getAssignedStagesByUserGroupId($userGroup->contextId, $userGroup->id)->toArray();
 
         switch ($columnId) {
             case 'name':
-                return ['label' => $userGroup->getLocalizedName()];
+                return ['label' => $userGroup->getLocalizedData('name')];
             case 'roleId':
-                $roleNames = Application::getRoleNames(false, [$userGroup->getRoleId()]);
+                $roleNames = Application::getRoleNames(false, [$userGroup->roleId]);
                 return ['label' => __(array_shift($roleNames))];
-            case in_array($columnId, $workflowStages):
-                // Set the state of the select element that will
-                // be used to assign the stage to the user group.
-                $selectDisabled = false;
-                if (in_array($columnId, $roleDao->getForbiddenStages($userGroup->getRoleId()))) {
-                    // This stage should not be assigned to the user group.
-                    $selectDisabled = true;
-                }
-
-                return ['selected' => in_array($columnId, $assignedStages),
-                    'disabled' => $selectDisabled];
             default:
+                if (in_array($columnId, $workflowStages)) {
+                    // Set the state of the select element that will
+                    // be used to assign the stage to the user group.
+                    $selectDisabled = false;
+                    if (in_array($columnId, $roleDao->getForbiddenStages($userGroup->roleId))) {
+                        // This stage should not be assigned to the user group.
+                        $selectDisabled = true;
+                    }
+
+                    return [
+                        'selected' => in_array($columnId, $assignedStages),
+                        'disabled' => $selectDisabled
+                    ];
+                }
                 break;
         }
 
@@ -82,12 +85,12 @@ public function getCellActions($request, $row, $column, $position = GridHandler:
         if (in_array($columnId, $workflowStages)) {
             $userGroup = $row->getData(); /** @var UserGroup $userGroup */
 
-            $assignedStages = Repo::userGroup()->getAssignedStagesByUserGroupId($userGroup->getContextId(), $userGroup->getId())->toArray();
+            $assignedStages = Repo::userGroup()->getAssignedStagesByUserGroupId($userGroup->contextId, $userGroup->id)->toArray();
 
             $router = $request->getRouter();
             $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
 
-            if (!in_array($columnId, $roleDao->getForbiddenStages($userGroup->getRoleId()))) {
+            if (!in_array($columnId, $roleDao->getForbiddenStages($userGroup->roleId))) {
                 if (in_array($columnId, $assignedStages)) {
                     $operation = 'unassignStage';
                     $actionTitleKey = 'grid.userGroup.unassignStage';
diff --git a/controllers/grid/settings/roles/UserGroupGridHandler.php b/controllers/grid/settings/roles/UserGroupGridHandler.php
index 77d7568149e..a18921c9203 100644
--- a/controllers/grid/settings/roles/UserGroupGridHandler.php
+++ b/controllers/grid/settings/roles/UserGroupGridHandler.php
@@ -81,6 +81,8 @@ public function authorize($request, &$args, $roleAssignments)
         $this->addPolicy(new ContextAccessPolicy($request, $roleAssignments));
 
         $operation = $request->getRequestedOp();
+        $context = $request->getContext();
+        $contextId = $context->getId();
         $workflowStageRequiredOps = ['assignStage', 'unassignStage'];
         if (in_array($operation, $workflowStageRequiredOps)) {
             $this->addPolicy(new WorkflowStageRequiredPolicy($request->getUserVar('stageId')));
@@ -91,7 +93,7 @@ public function authorize($request, &$args, $roleAssignments)
             // Validate the user group object.
             $userGroupId = $request->getUserVar('userGroupId');
 
-            $userGroup = Repo::userGroup()->get($userGroupId);
+            $userGroup = UserGroup::findById($userGroupId);
 
             if (!$userGroup) {
                 throw new \Exception('Invalid user group id!');
@@ -183,25 +185,30 @@ protected function loadData($request, $filter)
             $stageIdFilter = $filter['selectedStageId'];
         }
 
-        $rangeInfo = $this->getGridRangeInfo($request, $this->getId());
+        $query = UserGroup::withContextIds($contextId);
 
-        if ($stageIdFilter && $stageIdFilter != 0) {
-            return Repo::userGroup()->getCollector()
-                ->filterByContextIds([$contextId])
-                ->filterByStageIds([$stageIdFilter])
-                ->filterByRoleIds([$roleIdFilter])
-                ->limit($rangeInfo->getCount())
-                ->offset($rangeInfo->getOffset() + max(0, $rangeInfo->getPage() - 1) * $rangeInfo->getCount())
-                ->getMany()
-                ->toArray();
-        } elseif ($roleIdFilter && $roleIdFilter != 0) {
-            return Repo::userGroup()->getByRoleIds([$roleIdFilter], $contextId)->toArray();
-        } else {
-            return Repo::userGroup()->getCollector()
-                ->filterByContextIds([$contextId])
-                ->getMany()
-                ->toArray();
+        if (!empty($roleIdFilter)) {
+            $query->where('roleId', $roleIdFilter);
         }
+        
+        if (!empty($stageIdFilter)) {
+            $query->whereHas('userGroupStages', function ($q) use ($stageIdFilter) {
+                $q->where('stageId', $stageIdFilter);
+            });
+        }
+    
+        // pagination
+        $rangeInfo = $this->getGridRangeInfo($request, $this->getId());
+        $perPage = $rangeInfo->getCount();
+        $page = max(1, $rangeInfo->getPage());
+        $offset = ($page - 1) * $perPage;
+    
+        $query->offset($offset)->limit($perPage);
+    
+        // results
+        $userGroups = $query->get();
+    
+        return $userGroups;
     }
 
     /**
@@ -346,32 +353,29 @@ public function removeUserGroup($args, $request)
         $contextId = $this->_getContextId();
         $notificationMgr = new NotificationManager();
 
-        $usersAssignedToUserGroupCount = Repo::user()->getCollector()
-            ->filterByContextIds([$contextId])
-            ->filterByUserGroupIds([$userGroup->getId()])
-            ->getCount();
+        $usersAssignedToUserGroupCount = $userGroup->usersInContext($contextId)->count();
 
         if ($usersAssignedToUserGroupCount == 0) {
-            if ($userGroup->getData('isDefault')) {
+            if ($userGroup->isDefault) {
                 // Can't delete default user groups.
                 $notificationMgr->createTrivialNotification(
                     $user->getId(),
                     Notification::NOTIFICATION_TYPE_WARNING,
                     ['contents' => __(
                         'grid.userGroup.cantRemoveDefaultUserGroup',
-                        ['userGroupName' => $userGroup->getLocalizedName()	]
+                        ['userGroupName' => $userGroup->getLocalizedData('name')	]
                     )]
                 );
             } else {
                 // We can delete, no user assigned yet.
-                Repo::userGroup()->delete($userGroup);
+                $userGroup->delete();
 
                 $notificationMgr->createTrivialNotification(
                     $user->getId(),
                     Notification::NOTIFICATION_TYPE_SUCCESS,
                     ['contents' => __(
                         'grid.userGroup.removed',
-                        ['userGroupName' => $userGroup->getLocalizedName()	]
+                        ['userGroupName' => $userGroup->getLocalizedData('name')	]
                     )]
                 );
             }
@@ -383,12 +387,12 @@ public function removeUserGroup($args, $request)
                 Notification::NOTIFICATION_TYPE_WARNING,
                 ['contents' => __(
                     'grid.userGroup.cantRemoveUserGroup',
-                    ['userGroupName' => $userGroup->getLocalizedName(), 'usersCount' => $usersAssignedToUserGroupCount]
+                    ['userGroupName' => $userGroup->getLocalizedData('name'), 'usersCount' => $usersAssignedToUserGroupCount]
                 )]
             );
         }
 
-        $json = \PKP\db\DAO::getDataChangedEvent($userGroup->getId());
+        $json = \PKP\db\DAO::getDataChangedEvent($userGroup->id);
         $json->setGlobalEvent('userGroupUpdated');
         return $json;
     }
@@ -441,14 +445,18 @@ private function _toggleAssignment($args, $request)
             case 'assignStage':
                 UserGroupStage::create([
                     'contextId' => $contextId,
-                    'userGroupId' => $userGroup->getId(),
+                    'userGroupId' => $userGroup->id,
                     'stageId' => $stageId
                 ]);
 
                 $messageKey = 'grid.userGroup.assignedStage';
                 break;
             case 'unassignStage':
-                Repo::userGroup()->removeGroupFromStage($contextId, $userGroup->getId(), $stageId);
+                UserGroupStage::query()
+                    ->withContextId($contextId)
+                    ->withUserGroupId($userGroup->id)
+                    ->withStageId($stageId)
+                    ->delete();
                 $messageKey = 'grid.userGroup.unassignedStage';
                 break;
         }
@@ -463,11 +471,11 @@ private function _toggleAssignment($args, $request)
             Notification::NOTIFICATION_TYPE_SUCCESS,
             ['contents' => __(
                 $messageKey,
-                ['userGroupName' => $userGroup->getLocalizedName(), 'stageName' => __($stageLocaleKeys[$stageId])]
+                ['userGroupName' => $userGroup->getLocalizedData('name'), 'stageName' => __($stageLocaleKeys[$stageId])]
             )]
         );
 
-        return \PKP\db\DAO::getDataChangedEvent($userGroup->getId());
+        return \PKP\db\DAO::getDataChangedEvent($userGroup->id);
     }
 
     /**
diff --git a/controllers/grid/settings/roles/UserGroupGridRow.php b/controllers/grid/settings/roles/UserGroupGridRow.php
index 3e901abf924..609743e618a 100644
--- a/controllers/grid/settings/roles/UserGroupGridRow.php
+++ b/controllers/grid/settings/roles/UserGroupGridRow.php
@@ -41,7 +41,7 @@ public function initialize($request, $template = null)
 
         $rowId = $this->getId();
 
-        $actionArgs = ['userGroupId' => $userGroup->getId()];
+        $actionArgs = ['userGroupId' => $userGroup->id];
         $this->setRequestArgs($actionArgs);
 
         // Only add row actions if this is an existing row.
diff --git a/controllers/grid/settings/roles/form/UserGroupForm.php b/controllers/grid/settings/roles/form/UserGroupForm.php
index 3a9333ee0a8..dbe30262e3a 100644
--- a/controllers/grid/settings/roles/form/UserGroupForm.php
+++ b/controllers/grid/settings/roles/form/UserGroupForm.php
@@ -29,6 +29,11 @@
 use PKP\stageAssignment\StageAssignment;
 use PKP\userGroup\relationships\UserGroupStage;
 use PKP\workflow\WorkflowStageDAO;
+use PKP\userGroup\UserGroup;
+use PKP\userGroup\relationships\UserUserGroup;
+use PKP\userGroup\Repository as UserGroupRepository;
+use Illuminate\Support\Facades\App;
+use Illuminate\Support\Facades\DB;
 
 class UserGroupForm extends Form
 {
@@ -100,7 +105,7 @@ public function getLocaleFieldNames(): array
      */
     public function initData()
     {
-        $userGroup = Repo::userGroup()->get($this->getUserGroupId());
+        $userGroup = UserGroup::findById($this->getUserGroupId(), $this->getContextId());
         $stages = WorkflowStageDAO::getWorkflowStageTranslationKeys();
         $this->setData('stages', $stages);
         $this->setData('assignedStages', []); // sensible default
@@ -111,19 +116,19 @@ public function initData()
         $this->setData('roleForbiddenStagesJSON', $jsonMessage->getString());
 
         if ($userGroup) {
-            $assignedStages = Repo::userGroup()->getAssignedStagesByUserGroupId($this->getContextId(), $userGroup->getId())->toArray();
+            $assignedStages = $userGroup->getAssignedStageIds()->toArray();
 
             $data = [
-                'userGroupId' => $userGroup->getId(),
-                'roleId' => $userGroup->getRoleId(),
-                'name' => $userGroup->getName(null), //Localized
-                'abbrev' => $userGroup->getAbbrev(null), //Localized
+                'userGroupId' => $userGroup->id,
+                'roleId' => $userGroup->roleId,
+                'name' => $userGroup->name, // Localized array
+                'abbrev' => $userGroup->abbrev, // Localized array
                 'assignedStages' => $assignedStages,
-                'showTitle' => $userGroup->getShowTitle(),
-                'permitSelfRegistration' => $userGroup->getPermitSelfRegistration(),
-                'permitMetadataEdit' => $userGroup->getPermitMetadataEdit(),
-                'recommendOnly' => $userGroup->getRecommendOnly(),
-                'masthead' => $userGroup->getMasthead(),
+                'showTitle' => $userGroup->showTitle,
+                'permitSelfRegistration' => $userGroup->permitSelfRegistration,
+                'permitMetadataEdit' => $userGroup->permitMetadataEdit,
+                'recommendOnly' => $userGroup->recommendOnly,
+                'masthead' => $userGroup->masthead,
             ];
 
             foreach ($data as $field => $value) {
@@ -158,8 +163,8 @@ public function fetch($request, $template = null, $display = false)
         $templateMgr->assign('disableRoleSelect', $disableRoleSelect);
         $templateMgr->assign('selfRegistrationRoleIds', $this->getPermitSelfRegistrationRoles());
         $templateMgr->assign('recommendOnlyRoleIds', $this->getRecommendOnlyRoles());
-        $templateMgr->assign('notChangeMetadataEditPermissionRoles', Repo::userGroup()::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES);
-
+        $repository = Repo::userGroup();
+        $templateMgr->assign('notChangeMetadataEditPermissionRoles', $repository::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES);
         return parent::fetch($request, $template, $display);
     }
 
@@ -192,61 +197,82 @@ public function execute(...$functionParams)
 
         $request = Application::get()->getRequest();
         $userGroupId = $this->getUserGroupId();
-
         $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
 
+        $repository = Repo::userGroup();
+
         // Check if we are editing an existing user group or creating another one.
         if ($userGroupId == null) {
-            $userGroup = Repo::userGroup()->newDataObject();
+            // creating a new UserGroup
+            $userGroup = new UserGroup();
 
             $roleId = $this->getData('roleId');
             if ($roleId == Role::ROLE_ID_SITE_ADMIN) {
                 throw new \Exception('Site administrator roles cannot be created here.');
             }
-            $userGroup->setRoleId($roleId);
-
-            $userGroup->setContextId($this->getContextId());
-            $userGroup->setDefault(false);
-            $userGroup->setShowTitle(is_null($this->getData('showTitle')) ? false : $this->getData('showTitle'));
-            $userGroup->setPermitSelfRegistration($this->getData('permitSelfRegistration') && in_array($userGroup->getRoleId(), $this->getPermitSelfRegistrationRoles()));
-            $userGroup->setPermitMetadataEdit($this->getData('permitMetadataEdit') && !in_array($this->getData('roleId'), Repo::userGroup()::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES));
-            if (in_array($this->getData('roleId'), Repo::userGroup()::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES)) {
-                $userGroup->setPermitMetadataEdit(true);
+            $userGroup->roleId = $roleId;
+    
+            $userGroup->contextId = $this->getContextId();
+            $userGroup->isDefault = false;
+            $userGroup->showTitle = (bool) $this->getData('showTitle');
+            $userGroup->permitSelfRegistration = (bool) $this->getData('permitSelfRegistration') && in_array($userGroup->roleId, $this->getPermitSelfRegistrationRoles());
+
+            if (in_array($userGroup->roleId, Repo::userGroup()::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES)) {
+                $userGroup->permitMetadataEdit = true;
+            } else {
+                $userGroup->permitMetadataEdit = $this->getData('permitMetadataEdit') ?? false;
             }
 
-            $userGroup->setRecommendOnly($this->getData('recommendOnly') && in_array($userGroup->getRoleId(), $this->getRecommendOnlyRoles()));
+            $userGroup->recommendOnly = $this->getData('recommendOnly') && in_array($userGroup->roleId, $this->getRecommendOnlyRoles());
+            $userGroup->masthead = $this->getData('masthead') ?? false;
+
+            // set localized fields
             $userGroup = $this->_setUserGroupLocaleFields($userGroup, $request);
-            $userGroup->setMasthead($this->getData('masthead') ?? false);
-            $userGroupId = Repo::userGroup()->add($userGroup);
+
+            // save the user group
+            $userGroup->save();
+            $userGroupId = $userGroup->id;
         } else {
-            $userGroup = Repo::userGroup()->get($userGroupId);
+            // editing an existing UserGroup
+            $userGroup = UserGroup::findById($userGroupId, $this->getContextId());
+    
+            // update localized fields
             $userGroup = $this->_setUserGroupLocaleFields($userGroup, $request);
-            $userGroup->setShowTitle(is_null($this->getData('showTitle')) ? false : $this->getData('showTitle'));
-            $userGroup->setPermitSelfRegistration($this->getData('permitSelfRegistration') && in_array($userGroup->getRoleId(), $this->getPermitSelfRegistrationRoles()));
-            $userGroup->setPermitMetadataEdit($this->getData('permitMetadataEdit') && !in_array($userGroup->getRoleId(), Repo::userGroup()::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES));
-            if (in_array($userGroup->getRoleId(), Repo::userGroup()::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES)) {
-                $userGroup->setPermitMetadataEdit(true);
+    
+            $userGroup->showTitle = $this->getData('showTitle') ?? false;
+            $userGroup->permitSelfRegistration = $this->getData('permitSelfRegistration') && in_array($userGroup->roleId, $this->getPermitSelfRegistrationRoles());
+    
+            $previousPermitMetadataEdit = $userGroup->permitMetadataEdit;
+    
+            if (in_array($userGroup->roleId, $repository::NOT_CHANGE_METADATA_EDIT_PERMISSION_ROLES)) {
+                $userGroup->permitMetadataEdit = true;
             } else {
-                $permitMetadataEdit = $userGroup->getPermitMetadataEdit();
-
-                $stageAssignments = StageAssignment::withUserGroupId($userGroupId)
+                $userGroup->permitMetadataEdit = (bool) $this->getData('permitMetadataEdit');
+            }
+    
+            // if permitMetadataEdit has changed, update StageAssignments
+            if ($userGroup->permitMetadataEdit !== $previousPermitMetadataEdit) {
+                $stageAssignments = StageAssignment::query()
+                    ->withUserGroupId($userGroupId)
                     ->withContextId($this->getContextId())
                     ->get();
 
                 foreach ($stageAssignments as $stageAssignment) {
-                    $stageAssignment->update(['canChangeMetadata' => $permitMetadataEdit]);
+                    $stageAssignment->canChangeMetadata = $userGroup->permitMetadataEdit;
+                    $stageAssignment->save();
                 }
             }
 
-            $userGroup->setRecommendOnly($this->getData('recommendOnly') && in_array($userGroup->getRoleId(), $this->getRecommendOnlyRoles()));
-            $userGroup->setMasthead($this->getData('masthead') ?? false);
-            Repo::userGroup()->edit($userGroup, []);
+            $userGroup->recommendOnly = $this->getData('recommendOnly') && in_array($userGroup->roleId, $this->getRecommendOnlyRoles());
+            $userGroup->masthead = $this->getData('masthead') ?? false;
+            $userGroup->save();
         }
 
         // After we have created/edited the user group, we assign/update its stages.
         $assignedStages = $this->getData('assignedStages');
+
         // Always set all stages active for some permission levels.
-        if (in_array($userGroup->getRoleId(), $roleDao->getAlwaysActiveStages())) {
+        if (in_array($userGroup->roleId, $roleDao->getAlwaysActiveStages())) {
             $assignedStages = array_keys(WorkflowStageDAO::getWorkflowStageTranslationKeys());
         }
         if ($assignedStages) {
@@ -267,30 +293,35 @@ public function execute(...$functionParams)
     public function _assignStagesToUserGroup($userGroupId, $userAssignedStages)
     {
         $contextId = $this->getContextId();
+        $roleId = $this->getData('roleId');
+        $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
+        $stageIds = $this->getData('assignedStages') ?? [];
 
+    
         // Current existing workflow stages.
         $stages = WorkflowStageDAO::getWorkflowStageTranslationKeys();
-
-        foreach (array_keys($stages) as $stageId) {
-            Repo::userGroup()->removeGroupFromStage($contextId, $userGroupId, $stageId);
-        }
-
+    
+        // Remove all existing stage assignments for this user group
+        UserGroupStage::query()
+            ->withContextId($contextId)
+            ->withUserGroupId($userGroupId)
+            ->withStageIds($stageIds)
+            ->delete();
+    
+        // Assign new stages
         foreach ($userAssignedStages as $stageId) {
-            // Make sure we don't assign forbidden stages based on
-            // user groups role id. Override in case of some permission levels.
-            $roleId = $this->getData('roleId');
-            $roleDao = DAORegistry::getDAO('RoleDAO'); /** @var RoleDAO $roleDao */
+            // Make sure we don't assign forbidden stages based on user group role id
             $forbiddenStages = $roleDao->getForbiddenStages($roleId);
             if (in_array($stageId, $forbiddenStages) && !in_array($roleId, $roleDao->getAlwaysActiveStages())) {
                 continue;
             }
 
-            // Check if is a valid stage.
-            if (in_array($stageId, array_keys($stages))) {
+            // Check if it's a valid stage.
+            if (array_key_exists($stageId, $stages)) {
                 UserGroupStage::create([
                     'contextId' => $contextId,
                     'userGroupId' => $userGroupId,
-                    'stageId' => $stageId
+                    'stageId' => $stageId,
                 ]);
             } else {
                 throw new \Exception('Invalid stage id');
@@ -309,23 +340,23 @@ public function _setUserGroupLocaleFields($userGroup, $request): \PKP\userGroup\
     {
         $router = $request->getRouter();
         $context = $router->getContext($request);
-        $supportedLocales = $context->getSupportedLocaleNames();
-
+        $supportedLocales = $context->getSupportedLocales();
+        $name = $this->getData('name');
+        $abbrev = $this->getData('abbrev');
+    
         if (!empty($supportedLocales)) {
-            foreach ($context->getSupportedLocaleNames() as $localeKey => $localeName) {
-                $name = $this->getData('name');
-                $abbrev = $this->getData('abbrev');
+            foreach ($supportedLocales as $localeKey) {
                 if (isset($name[$localeKey])) {
-                    $userGroup->setName($name[$localeKey], $localeKey);
+                    $userGroup->name[$localeKey] = $name[$localeKey];
                 }
                 if (isset($abbrev[$localeKey])) {
-                    $userGroup->setAbbrev($abbrev[$localeKey], $localeKey);
+                    $userGroup->abbrev[$localeKey] = $abbrev[$localeKey];
                 }
             }
         } else {
             $localeKey = Locale::getLocale();
-            $userGroup->setName($this->getData('name'), $localeKey);
-            $userGroup->setAbbrev($this->getData('abbrev'), $localeKey);
+            $userGroup->name[$localeKey] = $name[$localeKey] ?? '';
+            $userGroup->abbrev[$localeKey] = $abbrev[$localeKey] ?? '';
         }
 
         return $userGroup;
diff --git a/controllers/grid/settings/sections/form/PKPSectionForm.php b/controllers/grid/settings/sections/form/PKPSectionForm.php
index 4cff4a8a3f8..16e77cb309e 100644
--- a/controllers/grid/settings/sections/form/PKPSectionForm.php
+++ b/controllers/grid/settings/sections/form/PKPSectionForm.php
@@ -112,18 +112,17 @@ public function setSection(Section $section): void
      */
     public function fetch($request, $template = null, $display = false)
     {
-        $assignableUserGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$request->getContext()->getId()])
-            ->filterByRoleIds($this->assignableRoles)
-            ->filterByStageIds([WORKFLOW_STAGE_ID_SUBMISSION])
-            ->getMany()
+        $assignableUserGroups = UserGroup::query()
+            ->withContextIds([$request->getContext()->getId()])
+            ->withRoleIds($this->assignableRoles)
+            ->withStageIds([WORKFLOW_STAGE_ID_SUBMISSION])
+            ->get()
             ->map(function (UserGroup $userGroup) use ($request) {
                 return [
                     'userGroup' => $userGroup,
                     'users' => Repo::user()
                         ->getCollector()
-                        ->filterByUserGroupIds([$userGroup->getId()])
+                        ->filterByUserGroupIds([$userGroup->id])
                         ->filterByContextIds([$request->getContext()->getId()])
                         ->getMany()
                         ->mapWithKeys(fn ($user, $key) => [$user->getId() => $user->getFullName()])
diff --git a/controllers/grid/settings/user/UserGridHandler.php b/controllers/grid/settings/user/UserGridHandler.php
index 6817b1f208c..cc256a26bd2 100644
--- a/controllers/grid/settings/user/UserGridHandler.php
+++ b/controllers/grid/settings/user/UserGridHandler.php
@@ -42,6 +42,7 @@
 use PKP\security\Validation;
 use PKP\user\User;
 use PKP\userGroup\UserGroup;
+use PKP\userGroup\relationships\UserUserGroup;
 
 class UserGridHandler extends GridHandler
 {
@@ -159,9 +160,18 @@ public function getTemplateVarsFromRow($row): array
                     $user = $row->getData();
                     assert($user instanceof User);
                     $contextId = Application::get()->getRequest()->getContext()->getId();
-                    $userGroupsIterator = Repo::userGroup()->userUserGroups($user->getId(), $contextId);
-                    $roles = $userGroupsIterator->map(fn (UserGroup $userGroup) => $userGroup->getLocalizedName())->join(__('common.commaListSeparator'));
-                    return ['label' => $roles];
+
+                    // fetch user groups where the user is assigned in the current context
+                    $userGroups = UserGroup::query()
+                    ->withContextIds($contextId)
+                    ->whereHas('userUserGroups', function ($query) use ($user) {
+                        $query->withUserId($user->getId())
+                              ->withActive();
+                    })
+                    ->get();
+                
+                $roles = $userGroups->map(fn (UserGroup $userGroup) => $userGroup->getLocalizedData('name'))->join(__('common.commaListSeparator'));
+                return ['label' => $roles];
                 }
             }
         );
@@ -239,12 +249,11 @@ public function renderFilter($request, $filterData = [])
     {
         $context = $request->getContext();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds([$context->getId()])->get();
+
         $userGroupOptions = ['' => __('grid.user.allRoles')];
         foreach ($userGroups as $userGroup) {
-            $userGroupOptions[$userGroup->getId()] = $userGroup->getLocalizedName();
+            $userGroupOptions[$userGroup->id] = $userGroup->getLocalizedData('name');
         }
 
         $userDao = Repo::user()->dao;
@@ -539,29 +548,39 @@ public function removeUser($args, $request)
         if (!$request->checkCSRF()) {
             return new JSONMessage(false);
         }
-
+    
         $context = $request->getContext();
         $user = $request->getUser();
-
+    
         // Identify the user Id.
         $userId = $request->getUserVar('rowId');
-
-        if ($userId !== null && Validation::getAdministrationLevel($userId, $user->getId(), $request->getContext()->getId()) === Validation::ADMINISTRATION_PROHIBITED) {
+    
+        if ($userId !== null && Validation::getAdministrationLevel($userId, $user->getId(), $context->getId()) === Validation::ADMINISTRATION_PROHIBITED) {
             // We don't have administrative rights over this user.
             return new JSONMessage(false, __('grid.user.cannotAdminister'));
         }
-
-        // End all active user group assignments for this context.
+    
         // Check if this user has any active user group assignments for this context.
-        $activeUserGroupCount = Repo::userGroup()
-            ->userUserGroups($userId, $context->getId())
+        $activeUserGroupCount = UserGroup::query()
+            ->withContextIds($context->getId())
+            ->whereHas('userUserGroups', function ($query) use ($userId) {
+                $query->withUserId($userId)
+                    ->withActive();
+            })
             ->count();
-
+        
         if (!$activeUserGroupCount) {
             return new JSONMessage(false, __('grid.user.userNoRoles'));
         } else {
-            Repo::userGroup()->endAssignments($context->getId(), $userId);
-
+            // End all active user group assignments for this context.
+            UserUserGroup::query()
+                ->withUserId($userId)
+                ->withActive()
+                ->whereHas('userGroup', function ($query) use ($context) {
+                    $query->withContextIds($context->getId());
+                })
+                ->update(['dateEnd' => now()]);
+        
             return \PKP\db\DAO::getDataChangedEvent($userId);
         }
     }
diff --git a/controllers/grid/settings/user/form/UserForm.php b/controllers/grid/settings/user/form/UserForm.php
index bd1eb02a097..a3b3113b1d5 100644
--- a/controllers/grid/settings/user/form/UserForm.php
+++ b/controllers/grid/settings/user/form/UserForm.php
@@ -20,6 +20,8 @@
 use APP\facades\Repo;
 use APP\template\TemplateManager;
 use PKP\form\Form;
+use PKP\userGroup\UserGroup;
+use PKP\userGroup\relationships\UserUserGroup;
 
 class UserForm extends Form
 {
@@ -50,11 +52,17 @@ public function initData()
         $userGroupIds = $masthead = [];
 
         if (!is_null($this->userId)) {
-            $userGroups = Repo::userGroup()->userUserGroups($this->userId);
-
+            // fetch user groups where the user is assigned
+            $userGroups = UserGroup::query()
+                ->whereHas('userUserGroups', function ($query) {
+                    $query->withUserId($this->userId)
+                          ->withActive();
+                })
+                ->get();
+    
             foreach ($userGroups as $userGroup) {
-                $userGroupIds[] = $userGroup->getId();
-                $masthead[$userGroup->getId()] = Repo::userGroup()->userOnMasthead($this->userId, $userGroup->getId());
+                $userGroupIds[] = $userGroup->id;
+                $masthead[$userGroup->id] = Repo::userGroup()->userOnMasthead($this->userId, $userGroup->id);
             }
         }
 
@@ -86,12 +94,10 @@ public function display($request = null, $template = null)
 
         $allUserGroups = [];
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$contextId])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds([$contextId])->get();
 
         foreach ($userGroups as $userGroup) {
-            $allUserGroups[(int) $userGroup->getId()] = $userGroup->getLocalizedName();
+            $allUserGroups[(int) $userGroup->id] = $userGroup->getLocalizedData('name');
         }
 
         $templateMgr->assign([
@@ -121,29 +127,36 @@ public function saveUserGroupAssignments(Request $request): void
 
         if ($this->getData('userGroupIds')) {
             $contextId = $request->getContext()->getId();
-
-            $oldUserGroupIds = [];
-            $oldUserGroups = Repo::userGroup()->userUserGroups($this->userId);
-            foreach ($oldUserGroups as $oldUserGroup) {
-                $oldUserGroupIds[] = $oldUserGroup->getId();
-            }
-
+    
+            // get current user group IDs
+            $oldUserGroupIds = UserGroup::query()
+                ->whereHas('userUserGroups', function ($query) {
+                    $query->withUserId($this->userId)
+                          ->withActive();
+                })
+                ->pluck('user_group_id')
+                ->all();
+    
             $userGroupsToEnd = array_diff($oldUserGroupIds, $this->getData('userGroupIds'));
             collect($userGroupsToEnd)
                 ->each(
                     fn ($userGroupId) =>
-                    Repo::userGroup()->contextHasGroup($contextId, $userGroupId)
-                        ? Repo::userGroup()->endAssignments($contextId, $this->userId, $userGroupId)
-                        : null
+                    UserUserGroup::query()
+                        ->withUserId($this->userId)
+                        ->withUserGroupId($userGroupId)
+                        ->withActive()
+                        ->update(['date_end' => now()])
                 );
 
             $userGroupsToAdd = array_diff($this->getData('userGroupIds'), $oldUserGroupIds);
             collect($userGroupsToAdd)
                 ->each(
                     fn ($userGroupId) =>
-                    Repo::userGroup()->contextHasGroup($contextId, $userGroupId)
-                        ? Repo::userGroup()->assignUserToGroup($this->userId, $userGroupId)
-                        : null
+                    UserUserGroup::create([
+                        'userId' => $this->userId,
+                        'userGroupId' => $userGroupId,
+                        'dateStart' => now(),
+                    ])
                 );
         }
     }
diff --git a/controllers/grid/users/exportableUsers/ExportableUsersGridHandler.php b/controllers/grid/users/exportableUsers/ExportableUsersGridHandler.php
index 2cda973f726..7d690e45c0f 100644
--- a/controllers/grid/users/exportableUsers/ExportableUsersGridHandler.php
+++ b/controllers/grid/users/exportableUsers/ExportableUsersGridHandler.php
@@ -28,6 +28,7 @@
 use PKP\linkAction\request\RedirectConfirmationModal;
 use PKP\security\authorization\ContextAccessPolicy;
 use PKP\security\Role;
+use PKP\userGroup\UserGroup;
 
 class ExportableUsersGridHandler extends GridHandler
 {
@@ -208,13 +209,11 @@ public function renderFilter($request, $filterData = [])
     {
         $context = $request->getContext();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds([$context->getId()])->get();
 
         $userGroupOptions = ['' => __('grid.user.allRoles')];
         foreach ($userGroups as $userGroup) {
-            $userGroupOptions[$userGroup->getId()] = $userGroup->getLocalizedName();
+            $userGroupOptions[$userGroup->id] = $userGroup->getLocalizedData('name');
         }
         $userDao = Repo::user()->dao;
         $fieldOptions = [
diff --git a/controllers/grid/users/reviewer/form/AdvancedSearchReviewerForm.php b/controllers/grid/users/reviewer/form/AdvancedSearchReviewerForm.php
index 3bb20cf6422..24d53eb669f 100644
--- a/controllers/grid/users/reviewer/form/AdvancedSearchReviewerForm.php
+++ b/controllers/grid/users/reviewer/form/AdvancedSearchReviewerForm.php
@@ -130,7 +130,7 @@ public function fetch($request, $template = null, $display = false)
         // Replaces StageAssignmentDAO::getBySubmissionAndStageId
         $warnOnAssignment = StageAssignment::withSubmissionIds([$this->getSubmissionId()])
             ->get()
-            ->pluck('userId')
+            ->pluck('user_id')
             ->all();
 
         // Get a list of users in the managerial and admin user groups
diff --git a/controllers/grid/users/reviewer/form/EnrollExistingReviewerForm.php b/controllers/grid/users/reviewer/form/EnrollExistingReviewerForm.php
index c52ea461294..cd5cba92ddf 100644
--- a/controllers/grid/users/reviewer/form/EnrollExistingReviewerForm.php
+++ b/controllers/grid/users/reviewer/form/EnrollExistingReviewerForm.php
@@ -123,12 +123,12 @@ protected function isValidUserAndGroup(int $userId, int $userGroupId): bool
         }
 
         // User Group refers to the reviewer role
-        if ($userGroup->getData('roleId') != Role::ROLE_ID_REVIEWER) {
+        if ($userGroup->roleId != Role::ROLE_ID_REVIEWER) {
             return false;
         }
 
         // User group refers to the right context
-        if (intval($userGroup->getData('contextId')) != $context->getId()) {
+        if ((int) $userGroup->contextId != $context->getId()) {
             return false;
         }
 
diff --git a/controllers/grid/users/reviewer/form/ReviewerForm.php b/controllers/grid/users/reviewer/form/ReviewerForm.php
index b677a3d2d7d..2f7fe7e9719 100644
--- a/controllers/grid/users/reviewer/form/ReviewerForm.php
+++ b/controllers/grid/users/reviewer/form/ReviewerForm.php
@@ -280,7 +280,7 @@ public function fetch($request, $template = null, $display = false)
 
         $userGroups = [];
         foreach ($reviewerUserGroups as $userGroup) {
-            $userGroups[$userGroup->getId()] = $userGroup->getLocalizedName();
+            $userGroups[$userGroup->id] = $userGroup->getLocalizedData('name');
         }
 
         $this->setData('userGroups', $userGroups);
diff --git a/controllers/grid/users/stageParticipant/StageParticipantGridCategoryRow.php b/controllers/grid/users/stageParticipant/StageParticipantGridCategoryRow.php
index ef2e534f657..ba9c1213098 100644
--- a/controllers/grid/users/stageParticipant/StageParticipantGridCategoryRow.php
+++ b/controllers/grid/users/stageParticipant/StageParticipantGridCategoryRow.php
@@ -48,7 +48,7 @@ public function __construct($submission, $stageId)
     public function getCategoryLabel()
     {
         $userGroup = $this->getData();
-        return $userGroup->getLocalizedName();
+        return $userGroup->getLocalizedData('name');
     }
 
     //
diff --git a/controllers/grid/users/stageParticipant/StageParticipantGridHandler.php b/controllers/grid/users/stageParticipant/StageParticipantGridHandler.php
index c7e058487f7..a21fb220521 100644
--- a/controllers/grid/users/stageParticipant/StageParticipantGridHandler.php
+++ b/controllers/grid/users/stageParticipant/StageParticipantGridHandler.php
@@ -203,7 +203,7 @@ public function loadCategoryData($request, &$userGroup, $filter = null)
         // Replaces StageAssignmentDAO::getBySubmissionAndStageId
         $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
             ->withStageIds([$stageId])
-            ->withUserGroupId($userGroup->getId())
+            ->withUserGroupId($userGroup->id)
             ->get();
 
         return $stageAssignments->mapWithKeys(function ($stageAssignment) {
@@ -279,13 +279,13 @@ protected function loadData($request, $filter)
             $this->getStageId()
         );
         foreach ($userGroups as $userGroup) {
-            if ($userGroup->getRoleId() == Role::ROLE_ID_REVIEWER) {
+            if ($userGroup->roleId == Role::ROLE_ID_REVIEWER) {
                 continue;
             }
-            if (!in_array($userGroup->getId(), $userGroupIds)) {
+            if (!in_array($userGroup->id, $userGroupIds)) {
                 continue;
             }
-            $result[$userGroup->getId()] = $userGroup;
+            $result[$userGroup->id] = $userGroup;
         }
         return $result;
     }
@@ -342,7 +342,7 @@ public function saveParticipant($args, $request)
 
             // Check user group role id.
             $userGroup = Repo::userGroup()->get($userGroupId);
-            if ($userGroup->getRoleId() == Role::ROLE_ID_MANAGER) {
+            if ($userGroup->roleId == Role::ROLE_ID_MANAGER) {
                 $notificationMgr->updateNotification(
                     $request,
                     $notificationMgr->getDecisionStageNotifications(),
@@ -389,7 +389,7 @@ public function saveParticipant($args, $request)
                 'dateLogged' => Core::getCurrentDate(),
                 'userFullName' => $assignedUser->getFullName(),
                 'username' => $assignedUser->getUsername(),
-                'userGroupName' => $userGroup->getData('name')
+                'userGroupName' => $userGroup->name,
             ]);
             Repo::eventLog()->add($eventLog);
 
@@ -463,7 +463,7 @@ public function deleteParticipant($args, $request)
             'dateLogged' => Core::getCurrentDate(),
             'userFullName' => $assignedUser->getFullName(),
             'username' => $assignedUser->getUsername(),
-            'userGroupName' => $userGroup->getData('name')
+            'userGroupName' => $userGroup->name,
         ]);
         Repo::eventLog()->add($eventLog);
 
@@ -491,7 +491,7 @@ public function fetchUserList($args, $request)
         $users = $collector->getMany();
 
         $userGroup = Repo::userGroup()->get($userGroupId);
-        $roleId = $userGroup->getRoleId();
+        $roleId = $userGroup->roleId;
 
         $sectionId = $submission->getSectionId();
         $contextId = $submission->getData('contextId');
diff --git a/controllers/grid/users/stageParticipant/StageParticipantGridRow.php b/controllers/grid/users/stageParticipant/StageParticipantGridRow.php
index aad852f8cca..a96f1536266 100644
--- a/controllers/grid/users/stageParticipant/StageParticipantGridRow.php
+++ b/controllers/grid/users/stageParticipant/StageParticipantGridRow.php
@@ -117,7 +117,7 @@ public function initialize($request, $template = null)
                 $dispatcher = $router->getDispatcher();
                 $userGroup = Repo::userGroup()->get($userGroupId);
 
-                if ($userGroup->getRoleId() == Role::ROLE_ID_AUTHOR) {
+                if ($userGroup->roleId == Role::ROLE_ID_AUTHOR) {
                     $handler = 'authorDashboard';
                     $op = 'submission';
                 } else {
diff --git a/controllers/grid/users/stageParticipant/form/AddParticipantForm.php b/controllers/grid/users/stageParticipant/form/AddParticipantForm.php
index 95ad8e3bf42..54723bd01b9 100644
--- a/controllers/grid/users/stageParticipant/form/AddParticipantForm.php
+++ b/controllers/grid/users/stageParticipant/form/AddParticipantForm.php
@@ -100,11 +100,11 @@ protected function _isChangePermitMetadataAllowed(UserGroup $userGroup, int $use
     {
         $currentUser = Application::get()->getRequest()->getUser();
 
-        if ($currentUser->getId() === $userId && $userGroup->getRoleId() === Role::ROLE_ID_SUB_EDITOR) {
+        if ($currentUser->getId() === $userId && $userGroup->roleId === Role::ROLE_ID_SUB_EDITOR) {
             return false;
         }
 
-        return $userGroup->getRoleId() !== Role::ROLE_ID_MANAGER;
+        return $userGroup->roleId !== Role::ROLE_ID_MANAGER;
     }
 
     /**
@@ -116,11 +116,11 @@ protected function _isChangeRecommendOnlyAllowed(UserGroup $userGroup, int $user
     {
         $currentUser = Application::get()->getRequest()->getUser();
 
-        if ($currentUser->getId() === $userId && $userGroup->getRoleId() === Role::ROLE_ID_SUB_EDITOR) {
+        if ($currentUser->getId() === $userId && $userGroup->roleId === Role::ROLE_ID_SUB_EDITOR) {
             return false;
         }
 
-        return in_array($userGroup->getRoleId(), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR]);
+        return in_array($userGroup->roleId, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR]);
     }
 
     /**
@@ -138,10 +138,10 @@ public function fetch($request, $template = null, $display = false)
         $userGroupOptions = [];
         foreach ($userGroups as $userGroup) {
             // Exclude reviewers.
-            if ($userGroup->getRoleId() == Role::ROLE_ID_REVIEWER) {
+            if ($userGroup->roleId == Role::ROLE_ID_REVIEWER) {
                 continue;
             }
-            $userGroupOptions[$userGroup->getId()] = $userGroup->getLocalizedName();
+            $userGroupOptions[$userGroup->id] = $userGroup->getLocalizedData('name');
         }
 
         $templateMgr = TemplateManager::getManager($request);
@@ -150,21 +150,22 @@ public function fetch($request, $template = null, $display = false)
             'userGroupOptions' => $userGroupOptions,
             'selectedUserGroupId' => array_shift($keys), // assign the first element as selected
             'possibleRecommendOnlyUserGroupIds' => $this->_possibleRecommendOnlyUserGroupIds,
-            'recommendOnlyUserGroupIds' => Repo::userGroup()->getCollector()
-                ->filterByContextIds([$request->getContext()->getId()])
-                ->filterByIsRecommendOnly()
-                ->getIds()
+            'recommendOnlyUserGroupIds' => UserGroup::query()
+                ->withContextIds($request->getContext()->getId())
+                ->isRecommendOnly(true)
+                ->pluck('user_group_id')
                 ->toArray(),
             'notPossibleEditSubmissionMetadataPermissionChange' => $this->_managerGroupIds,
-            'permitMetadataEditUserGroupIds' => Repo::userGroup()->getCollector()
-                ->filterByContextIds([$request->getContext()->getId()])
-                ->filterByPermitMetadataEdit(true)
-                ->getIds()
+            'permitMetadataEditUserGroupIds' => UserGroup::query()
+                ->withContextIds($request->getContext()->getId())
+                ->permitMetadataEdit(true)
+                ->pluck('user_group_id')
                 ->toArray(),
             'submissionId' => $this->getSubmission()->getId(),
             'userGroupId' => '',
             'userIdSelected' => '',
         ]);
+        
 
         if ($this->_assignmentId) {
             $stageAssignment = StageAssignment::find($this->_assignmentId);
@@ -177,7 +178,7 @@ public function fetch($request, $template = null, $display = false)
             $templateMgr->assign([
                 'assignmentId' => $this->_assignmentId,
                 'currentUserName' => $currentUser->getFullName(),
-                'currentUserGroup' => $userGroup->getLocalizedName(),
+                'currentUserGroup' => $userGroup->getLocalizedData('name'),
                 'userGroupId' => $stageAssignment->userGroupId,
                 'userIdSelected' => $stageAssignment->userId,
                 'currentAssignmentRecommendOnly' => $stageAssignment->recommendOnly,
@@ -257,7 +258,7 @@ public function execute(...$functionParams)
         $canChangeMetadata = $this->_isChangePermitMetadataAllowed($userGroup, $userId) ? (bool) $this->getData('canChangeMetadata') : true;
 
         // sanity check
-        if (UserGroupStage::withStageId($this->getStageId())->withUserGroupId($userGroup->getId())->get()->isNotEmpty()) {
+        if (UserGroupStage::withStageId($this->getStageId())->withUserGroupId($userGroup->id)->get()->isNotEmpty()) {
             $updated = false;
 
             if ($this->_assignmentId) {
@@ -276,7 +277,7 @@ public function execute(...$functionParams)
                 $stageAssignment = Repo::stageAssignment()
                     ->build(
                         $submission->getId(), 
-                        $userGroup->getId(), 
+                        $userGroup->id, 
                         $userId, 
                         $recommendOnly, 
                         $canChangeMetadata
@@ -285,7 +286,7 @@ public function execute(...$functionParams)
         }
 
         parent::execute(...$functionParams);
-        return [$userGroup->getId(), $userId, $stageAssignment->id];
+        return [$userGroup->id, $userId, $stageAssignment->id];
     }
 
     /**
diff --git a/controllers/grid/users/userSelect/UserSelectGridHandler.php b/controllers/grid/users/userSelect/UserSelectGridHandler.php
index 1da9cfa9ba6..1210dbd4949 100644
--- a/controllers/grid/users/userSelect/UserSelectGridHandler.php
+++ b/controllers/grid/users/userSelect/UserSelectGridHandler.php
@@ -76,10 +76,10 @@ public function initialize($request, $args = null)
         $this->_userGroupOptions = [];
         foreach ($userGroups as $userGroup) {
             // Exclude reviewers.
-            if ($userGroup->getRoleId() == Role::ROLE_ID_REVIEWER) {
+            if ($userGroup->roleId == Role::ROLE_ID_REVIEWER) {
                 continue;
             }
-            $this->_userGroupOptions[$userGroup->getId()] = $userGroup->getLocalizedName();
+            $this->_userGroupOptions[$userGroup->id] = $userGroup->getLocalizedData('name');
         }
 
         $this->setTitle('editor.submission.findAndSelectUser');
@@ -103,12 +103,14 @@ public function initialize($request, $args = null)
                 null,
                 null,
                 $cellProvider,
-                ['alignment' => GridColumn::COLUMN_ALIGNMENT_LEFT,
+                [
+                    'alignment' => GridColumn::COLUMN_ALIGNMENT_LEFT,
                     'width' => 30
                 ]
             )
         );
     }
+    
 
 
     //
diff --git a/controllers/modals/submission/ViewSubmissionMetadataHandler.php b/controllers/modals/submission/ViewSubmissionMetadataHandler.php
index 1e6cd48669b..4e133a81d55 100644
--- a/controllers/modals/submission/ViewSubmissionMetadataHandler.php
+++ b/controllers/modals/submission/ViewSubmissionMetadataHandler.php
@@ -22,6 +22,7 @@
 use PKP\security\authorization\SubmissionAccessPolicy;
 use PKP\security\Role;
 use PKP\submission\reviewAssignment\ReviewAssignment;
+use PKP\userGroup\UserGroup;
 
 class ViewSubmissionMetadataHandler extends handler
 {
@@ -53,11 +54,9 @@ public function display($args, $request)
         $context = $request->getContext();
         $templateMgr = TemplateManager::getManager($request);
         $publication = $submission->getCurrentPublication();
-
+        
         if ($reviewAssignment->getReviewMethod() != ReviewAssignment::SUBMISSION_REVIEW_METHOD_DOUBLEANONYMOUS) { /* ReviewAssignment::SUBMISSION_REVIEW_METHOD_ANONYMOUS or _OPEN */
-            $userGroups = Repo::userGroup()->getCollector()
-                ->filterByContextIds([$context->getId()])
-                ->getMany();
+            $userGroups = UserGroup::withContextIds([$context->getId()])->get();
 
             $templateMgr->assign('authors', $publication->getAuthorString($userGroups));
 
diff --git a/pages/about/AboutContextHandler.php b/pages/about/AboutContextHandler.php
index 30ae3c46f6d..0bc051e6098 100644
--- a/pages/about/AboutContextHandler.php
+++ b/pages/about/AboutContextHandler.php
@@ -28,6 +28,7 @@
 use PKP\security\Role;
 use PKP\userGroup\relationships\enums\UserUserGroupStatus;
 use PKP\userGroup\relationships\UserUserGroup;
+use PKP\userGroup\UserGroup;
 
 class AboutContextHandler extends Handler
 {
@@ -59,6 +60,24 @@ public function index($args, $request)
         $templateMgr->display('frontend/pages/about.tpl');
     }
 
+
+    private function getSortedMastheadUserGroups($context)
+    {
+        $mastheadUserGroups = UserGroup::withContextIds([$context->getId()])
+            ->masthead(true)
+            ->excludeRoles([Role::ROLE_ID_REVIEWER])
+            ->get();
+    
+        $savedOrder = (array) $context->getData('mastheadUserGroupIds');
+    
+        $sortedUserGroups = $mastheadUserGroups->sortBy(function ($userGroup) use ($savedOrder) {
+            return array_search($userGroup->id, $savedOrder);
+        });
+    
+        return $sortedUserGroups;
+    }
+    
+
     /**
      * Display editorial masthead page.
      *
@@ -70,35 +89,28 @@ public function index($args, $request)
     public function editorialMasthead($args, $request)
     {
         $context = $request->getContext();
-
-        $savedMastheadUserGroupIdsOrder = (array) $context->getData('mastheadUserGroupIds');
-
-        $collector = Repo::userGroup()->getCollector();
-        $allMastheadUserGroups = $collector
-            ->filterByContextIds([$context->getId()])
-            ->filterByMasthead(true)
-            ->filterExcludeRoles([Role::ROLE_ID_REVIEWER])
-            ->orderBy($collector::ORDERBY_ROLE_ID)
-            ->getMany()
-            ->toArray();
-
-        // sort the masthead roles in their saved order for display
-        $mastheadRoles = array_replace(array_intersect_key(array_flip($savedMastheadUserGroupIdsOrder), $allMastheadUserGroups), $allMastheadUserGroups);
-
-        $allUsersIdsGroupedByUserGroupId = Repo::userGroup()->getMastheadUserIdsByRoleIds($mastheadRoles, $context->getId());
-
+    
+        // Get sorted masthead roles using the extracted method
+        $mastheadRoles = $this->getSortedMastheadUserGroups($context);
+    
+        // Get all user IDs grouped by user group ID for the masthead roles
+        $allUsersIdsGroupedByUserGroupId = Repo::userGroup()->getMastheadUserIdsByRoleIds(
+            $mastheadRoles,
+            $context->getId()
+        );
+    
         $mastheadUsers = [];
-        foreach ($mastheadRoles as $mastheadUserGroup) {
-            foreach ($allUsersIdsGroupedByUserGroupId[$mastheadUserGroup->getId()] ?? [] as $userId) {
+        foreach ($mastheadRoles as $userGroupId => $mastheadUserGroup) {
+            foreach ($allUsersIdsGroupedByUserGroupId[$userGroupId] ?? [] as $userId) {
                 $user = Repo::user()->get($userId);
                 $userUserGroup = UserUserGroup::withUserId($user->getId())
-                    ->withUserGroupId($mastheadUserGroup->getId())
+                    ->withUserGroupId($userGroupId)
                     ->withActive()
                     ->withMasthead()
                     ->first();
                 if ($userUserGroup) {
                     $startDatetime = new DateTime($userUserGroup->dateStart);
-                    $mastheadUsers[$mastheadUserGroup->getId()][$user->getId()] = [
+                    $mastheadUsers[$userGroupId][$user->getId()] = [
                         'user' => $user,
                         'dateStart' => $startDatetime->format('Y'),
                     ];
@@ -111,7 +123,11 @@ public function editorialMasthead($args, $request)
         $usersCollector = Repo::user()->getCollector();
         $reviewers = $usersCollector
             ->filterByUserIds($reviewerIds->toArray())
-            ->orderBy($usersCollector::ORDERBY_FAMILYNAME, $usersCollector::ORDER_DIR_ASC, [Locale::getLocale(), Application::get()->getRequest()->getSite()->getPrimaryLocale()])
+            ->orderBy(
+                $usersCollector::ORDERBY_FAMILYNAME,
+                $usersCollector::ORDER_DIR_ASC,
+                [Locale::getLocale(), Application::get()->getRequest()->getSite()->getPrimaryLocale()]
+            )
             ->getMany();
 
         Hook::call('AboutContextHandler::editorialMasthead', [$mastheadRoles, $mastheadUsers, $reviewers, $previousYear]);
@@ -140,31 +156,25 @@ public function editorialHistory($args, $request)
     {
         $context = $request->getContext();
 
-        $savedMastheadUserGroupIdsOrder = (array) $context->getData('mastheadUserGroupIds');
-
-        $collector = Repo::userGroup()->getCollector();
-        $allMastheadUserGroups = $collector
-            ->filterByContextIds([$context->getId()])
-            ->filterByMasthead(true)
-            ->filterExcludeRoles([Role::ROLE_ID_REVIEWER])
-            ->orderBy($collector::ORDERBY_ROLE_ID)
-            ->getMany()
-            ->toArray();
-
-        // sort the masthead roles in their saved order for display
-        $mastheadRoles = array_replace(array_intersect_key(array_flip($savedMastheadUserGroupIdsOrder), $allMastheadUserGroups), $allMastheadUserGroups);
-
-        $allUsersIdsGroupedByUserGroupId = Repo::userGroup()->getMastheadUserIdsByRoleIds($mastheadRoles, $context->getId(), UserUserGroupStatus::STATUS_ENDED);
+        // get sorted masthead roles using the extracted method
+        $mastheadRoles = $this->getSortedMastheadUserGroups($context);
+    
+        // get all user IDs grouped by user group ID for the masthead roles with ended status
+        $allUsersIdsGroupedByUserGroupId = Repo::userGroup()->getMastheadUserIdsByRoleIds(
+            $mastheadRoles,
+            $context->getId(),
+            UserUserGroupStatus::STATUS_ENDED
+        );
 
         $mastheadUsers = [];
-        foreach ($mastheadRoles as $mastheadUserGroup) {
-            foreach ($allUsersIdsGroupedByUserGroupId[$mastheadUserGroup->getId()] ?? [] as $userId) {
+        foreach ($mastheadRoles as $userGroupId => $mastheadUserGroup) {
+            foreach ($allUsersIdsGroupedByUserGroupId[$userGroupId] ?? [] as $userId) {
                 $user = Repo::user()->get($userId);
                 $userUserGroups = UserUserGroup::withUserId($user->getId())
-                    ->withUserGroupId($mastheadUserGroup->getId())
+                    ->withUserGroupId($userGroupId)
                     ->withEnded()
                     ->withMasthead()
-                    ->sortBy('date_start', 'desc')
+                    ->orderBy('date_start', 'desc')
                     ->get();
                 $services = [];
                 foreach ($userUserGroups as $userUserGroup) {
@@ -176,7 +186,7 @@ public function editorialHistory($args, $request)
                     ];
                 }
                 if (!empty($services)) {
-                    $mastheadUsers[$mastheadUserGroup->getId()][$user->getId()] = [
+                    $mastheadUsers[$userGroupId][$user->getId()] = [
                         'user' => $user,
                         'services' => $services
                     ];
diff --git a/pages/admin/AdminHandler.php b/pages/admin/AdminHandler.php
index c498c4f6d91..d93b5ca5527 100644
--- a/pages/admin/AdminHandler.php
+++ b/pages/admin/AdminHandler.php
@@ -53,6 +53,7 @@
 use PKP\security\Role;
 use PKP\site\VersionCheck;
 use PKP\site\VersionDAO;
+use PKP\userGroup\UserGroup;
 
 class AdminHandler extends Handler
 {
@@ -322,9 +323,7 @@ public function wizard($args, $request)
 
         $bulkEmailsEnabled = in_array($context->getId(), (array) $request->getSite()->getData('enableBulkEmails'));
         if ($bulkEmailsEnabled) {
-            $userGroups = Repo::userGroup()->getCollector()
-                ->filterByContextIds([$context->getId()])
-                ->getMany();
+            $userGroups = UserGroup::withContextIds([$context->getId()])->get()->toArray();
 
             $restrictBulkEmailsForm = new \PKP\components\forms\context\PKPRestrictBulkEmailsForm($apiUrl, $context, $userGroups);
             $components[$restrictBulkEmailsForm->id] = $restrictBulkEmailsForm->getConfig();
diff --git a/pages/catalog/PKPCatalogHandler.php b/pages/catalog/PKPCatalogHandler.php
index c23fe4ffe57..d2111e8f462 100644
--- a/pages/catalog/PKPCatalogHandler.php
+++ b/pages/catalog/PKPCatalogHandler.php
@@ -27,6 +27,7 @@
 use PKP\file\ContextFileManager;
 use PKP\security\authorization\ContextRequiredPolicy;
 use PKP\security\Role;
+use PKP\userGroup\UserGroup;
 
 class PKPCatalogHandler extends Handler
 {
@@ -105,9 +106,10 @@ public function category($args, $request)
             'parentCategory' => $parentCategory,
             'subcategories' => iterator_to_array($subcategories),
             'publishedSubmissions' => $submissions->toArray(),
-            'authorUserGroups' => Repo::userGroup()->getCollector()
-                ->filterByRoleIds([Role::ROLE_ID_AUTHOR])
-                ->filterByContextIds([$context->getId()])->getMany()->remember(),
+            'authorUserGroups' => UserGroup::withRoleIds([Role::ROLE_ID_AUTHOR])
+                ->withContextIds([$context->getId()])
+                ->get()
+                ->remember(),
         ]);
 
         return $templateMgr->display('frontend/pages/catalogCategory.tpl');
diff --git a/pages/dashboard/DashboardHandler.php b/pages/dashboard/DashboardHandler.php
index 0b4ca4eb858..481df105850 100644
--- a/pages/dashboard/DashboardHandler.php
+++ b/pages/dashboard/DashboardHandler.php
@@ -28,6 +28,7 @@
 use PKP\submission\GenreDAO;
 use PKP\submission\PKPSubmission;
 use PKP\config\Config;
+use PKP\userGroup\UserGroup;
 
 define('SUBMISSIONS_LIST_ACTIVE', 'active');
 define('SUBMISSIONS_LIST_ARCHIVE', 'archive');
@@ -116,9 +117,8 @@ public function index($args, $request)
         $itemsMax = $collector->getCount();
         $items = $collector->limit(30)->getMany();
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds([$context->getId()])
+        ->lazy();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
diff --git a/pages/decision/DecisionHandler.php b/pages/decision/DecisionHandler.php
index def944c3d6e..e6400be7ac0 100644
--- a/pages/decision/DecisionHandler.php
+++ b/pages/decision/DecisionHandler.php
@@ -123,7 +123,7 @@ public function record($args, $request)
                 ->withRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SUB_EDITOR])
                 ->withRecommendOnly(false)
                 ->get()
-                ->pluck('userId')
+                ->pluck('user_id')
                 ->all();
 
             if (!$assignedEditorIds) {
diff --git a/pages/management/ManagementHandler.php b/pages/management/ManagementHandler.php
index ea30a86287e..01be98195ef 100644
--- a/pages/management/ManagementHandler.php
+++ b/pages/management/ManagementHandler.php
@@ -147,25 +147,25 @@ public function context($args, $request)
         $this->setupTemplate($request);
         $context = $request->getContext();
         $dispatcher = $request->getDispatcher();
-
+    
         $apiUrl = $this->getContextApiUrl($request);
         $publicFileApiUrl = $dispatcher->url($request, PKPApplication::ROUTE_API, $context->getPath(), '_uploadPublicFile');
-
+    
         $locales = $this->getSupportedFormLocales($context);
-
+    
         $contactForm = new PKPContactForm($apiUrl, $locales, $context);
         $mastheadForm = new MastheadForm($apiUrl, $locales, $context, $publicFileApiUrl);
-
+    
         $templateMgr->setState([
             'components' => [
                 PKPContactForm::FORM_CONTACT => $contactForm->getConfig(),
                 MastheadForm::FORM_MASTHEAD => $mastheadForm->getConfig(),
             ],
         ]);
-
+    
         // Interact with the beacon (if enabled) and determine if a new version exists
         $latestVersion = VersionCheck::checkIfNewVersionExists();
-
+    
         // Display a warning message if there is a new version of OJS available
         if (Config::getVar('general', 'show_upgrade_warning') && $latestVersion) {
             $currentVersion = VersionCheck::getCurrentDBVersion();
@@ -175,24 +175,22 @@ public function context($args, $request)
                 'latestVersion' => $latestVersion,
             ]);
 
-            // Get contact information for site administrator
-            $userGroups = Repo::userGroup()->getByRoleIds([Role::ROLE_ID_SITE_ADMIN], PKPApplication::SITE_CONTEXT_ID);
-            $adminUserGroup = $userGroups->first();
-
-            $siteAdmin = Repo::user()->getCollector()
-                ->filterByUserGroupIds([$adminUserGroup->getId()])
-                ->getMany()
-                ->first();
+            $siteAdmins = Repo::user()->getCollector()
+                ->filterByRoleIds([Role::ROLE_ID_SITE_ADMIN])
+                ->getMany();
+            
+            $siteAdmin = $siteAdmins->first();
             $templateMgr->assign('siteAdmin', $siteAdmin);
         }
-
+    
         $templateMgr->assign('pageTitle', __('manager.setup'));
-
+    
         $templateMgr->registerClass(PKPContactForm::class, PKPContactForm::class); // FORM_CONTACT
         $templateMgr->registerClass(PKPMastheadForm::class, PKPMastheadForm::class); // FORM_MASTHEAD
-
+    
         $templateMgr->display('management/context.tpl');
     }
+    
 
     /**
      * Display website settings
diff --git a/pages/submission/PKPSubmissionHandler.php b/pages/submission/PKPSubmissionHandler.php
index 3bc2b037e64..4a5afa209aa 100644
--- a/pages/submission/PKPSubmissionHandler.php
+++ b/pages/submission/PKPSubmissionHandler.php
@@ -43,6 +43,7 @@
 use PKP\submission\GenreDAO;
 use PKP\submissionFile\SubmissionFile;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 abstract class PKPSubmissionHandler extends Handler
 {
@@ -197,10 +198,9 @@ protected function showWizard(array $args, Request $request, Submission $submiss
         $orderedLocales = $supportedLocales;
         uksort($orderedLocales, fn ($a, $b) => $b === $submission->getData('locale') ? 1 : -1);
 
-        $userGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::query()
+            ->withContextIds([$context->getId()])
+            ->get();
 
         /** @var GenreDAO $genreDao */
         $genreDao = DAORegistry::getDAO('GenreDAO');
@@ -219,6 +219,10 @@ protected function showWizard(array $args, Request $request, Submission $submiss
 
         $templateMgr = TemplateManager::getManager($request);
 
+        if (!$userGroups instanceof LazyCollection) {
+            $userGroups = $userGroups->lazy();
+        }
+
         $templateMgr->setState([
             'categories' => Repo::category()->getBreadcrumbs($categories),
             'components' => [
@@ -489,24 +493,23 @@ protected function getContributorsListPanel(Request $request, Submission $submis
      */
     protected function getSubmitUserGroups(Context $context, User $user): LazyCollection
     {
-        $userGroups = Repo::userGroup()
-            ->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->filterByUserIds([$user->getId()])
-            ->filterByRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN, Role::ROLE_ID_AUTHOR])
-            ->getMany();
+        $userGroups = UserGroup::query()
+            ->withContextIds([$context->getId()])
+            ->withUserIds([$user->getId()])
+            ->withRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN, Role::ROLE_ID_AUTHOR])
+            ->cursor();
 
         // Users without a submitting role can submit as an
         // author role that allows self registration
-        if (!$userGroups->count()) {
+        if ($userGroups->isEmpty()) {
             $defaultUserGroup = Repo::userGroup()->getFirstSubmitAsAuthorUserGroup($context->getId());
             return LazyCollection::make(function () use ($defaultUserGroup) {
                 if ($defaultUserGroup) {
-                    yield $defaultUserGroup->getId() => $defaultUserGroup;
+                    yield $defaultUserGroup->id => $defaultUserGroup;
                 }
             });
         }
-
+        
         return $userGroups;
     }
 
diff --git a/pages/workflow/PKPWorkflowHandler.php b/pages/workflow/PKPWorkflowHandler.php
index 59f06dd1fe1..67b6665e1c2 100644
--- a/pages/workflow/PKPWorkflowHandler.php
+++ b/pages/workflow/PKPWorkflowHandler.php
@@ -56,6 +56,7 @@
 use PKP\user\User;
 use PKP\workflow\WorkflowStageDAO;
 use PKP\config\Config;
+use PKP\userGroup\UserGroup;
 
 abstract class PKPWorkflowHandler extends Handler
 {
@@ -165,9 +166,6 @@ public function index($args, $request)
         $workflowRoles = Application::getWorkflowTypeRoles();
         $editorialWorkflowRoles = $workflowRoles[PKPApplication::WORKFLOW_TYPE_EDITORIAL];
 
-        $result = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$submission->getData('contextId')])
-            ->getMany();
         $authorUserGroups = Repo::userGroup()->getByRoleIds([Role::ROLE_ID_AUTHOR], $submission->getData('contextId'));
         $workflowUserGroups = Repo::userGroup()->getByRoleIds($editorialWorkflowRoles, $submission->getData('contextId'));
 
@@ -177,14 +175,14 @@ public function index($args, $request)
         // they are not assigned in any role and have a manager role in the
         // context.
         $currentStageId = $submission->getData('stageId');
-        $accessibleWorkflowStages = $this->getAuthorizedContextObject(Application::ASSOC_TYPE_ACCESSIBLE_WORKFLOW_STAGES);
         $canAccessPublication = false; // View title, metadata, etc.
         $canEditPublication = Repo::submission()->canEditPublication($submission->getId(), $request->getUser()->getId());
         $canAccessProduction = false; // Access to galleys and issue entry
         $canPublish = false; // Ability to publish, unpublish and create versions
         $canAccessEditorialHistory = false; // Access to activity log
+        $accessibleRoles = $this->getAuthorizedContextObject(Application::ASSOC_TYPE_USER_ROLES) ?? [];
         // unassigned managers
-        if (!$accessibleWorkflowStages && array_intersect($this->getAuthorizedContextObject(Application::ASSOC_TYPE_USER_ROLES), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN] ?? [])) {
+        if (!$accessibleWorkflowStages && array_intersect($accessibleRoles, [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN])) {
             $canAccessProduction = true;
             $canPublish = true;
             $canAccessPublication = true;
@@ -194,7 +192,8 @@ public function index($args, $request)
             $canAccessPublication = true;
 
             // Replaces StageAssignmentDAO::getBySubmissionAndUserIdAndStageId
-            $stageAssignments = StageAssignment::withSubmissionIds([$submission->getId()])
+            $stageAssignments = StageAssignment::query()
+                ->withSubmissionIds([$submission->getId()])
                 ->withUserId($request->getUser()->getId())
                 ->withStageIds([WORKFLOW_STAGE_ID_PRODUCTION])
                 ->get();
@@ -204,14 +203,11 @@ public function index($args, $request)
             // have been granted access and should be allowed to publish.
             if ($stageAssignments->isEmpty() && is_array($accessibleWorkflowStages[WORKFLOW_STAGE_ID_PRODUCTION] ?? null)) {
                 $canPublish = (bool) array_intersect([Role::ROLE_ID_SITE_ADMIN, Role::ROLE_ID_MANAGER], $accessibleWorkflowStages[WORKFLOW_STAGE_ID_PRODUCTION]);
-
-                // Otherwise, check stage assignments
-                // "Recommend only" stage assignments can not publish
             } else {
                 foreach ($stageAssignments as $stageAssignment) {
                     foreach ($workflowUserGroups as $workflowUserGroup) {
-                        if ($stageAssignment->userGroupId == $workflowUserGroup->getId() &&
-                                !$stageAssignment->recommendOnly) {
+                        if ($stageAssignment->userGroupId == $workflowUserGroup->usergroupid &&
+                            !$stageAssignment->recommendOnly) {
                             $canPublish = true;
                             break;
                         }
@@ -580,14 +576,17 @@ public function editorDecisionActions($args, $request)
         // see if the user is manager, and
         // if the group is recommendOnly
         if (!$makeRecommendation && !$makeDecision) {
-            $userGroups = Repo::userGroup()->userUserGroups($user->getId(), $request->getContext()->getId());
+            $userGroups = UserGroup::query()
+                ->withContextIds([$request->getContext()->getId()])
+                ->withUserIds([$user->getId()])
+                ->withRoleIds([Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN])
+                ->get();
+    
             foreach ($userGroups as $userGroup) {
-                if (in_array($userGroup->getRoleId(), [Role::ROLE_ID_MANAGER, Role::ROLE_ID_SITE_ADMIN])) {
-                    if (!$userGroup->getRecommendOnly()) {
-                        $makeDecision = true;
-                    } else {
-                        $makeRecommendation = true;
-                    }
+                if (!$userGroup->recommendOnly) {
+                    $makeDecision = true;
+                } else {
+                    $makeRecommendation = true;
                 }
             }
         }
diff --git a/plugins/importexport/native/filter/NativeXmlPKPAuthorFilter.php b/plugins/importexport/native/filter/NativeXmlPKPAuthorFilter.php
index 3183fd96a9b..a0fc0db4352 100644
--- a/plugins/importexport/native/filter/NativeXmlPKPAuthorFilter.php
+++ b/plugins/importexport/native/filter/NativeXmlPKPAuthorFilter.php
@@ -22,6 +22,7 @@
 use Exception;
 use PKP\facades\Locale;
 use PKP\filter\FilterGroup;
+use PKP\userGroup\UserGroup;
 
 class NativeXmlPKPAuthorFilter extends NativeImportFilter
 {
@@ -147,14 +148,12 @@ public function handleElement($node)
         // Identify the user group by name
         $userGroupName = $node->getAttribute('user_group_ref');
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds([$context->getId()])->get();
 
         foreach ($userGroups as $userGroup) {
             if (in_array($userGroupName, $userGroup->getName(null))) {
                 // Found a candidate; stash it.
-                $author->setUserGroupId($userGroup->getId());
+                $author->setUserGroupId($userGroup->id);
                 break;
             }
         }
diff --git a/plugins/importexport/users/filter/NativeXmlUserGroupFilter.php b/plugins/importexport/users/filter/NativeXmlUserGroupFilter.php
index b8934620b9a..8391ada57e9 100644
--- a/plugins/importexport/users/filter/NativeXmlUserGroupFilter.php
+++ b/plugins/importexport/users/filter/NativeXmlUserGroupFilter.php
@@ -20,6 +20,8 @@
 use PKP\filter\FilterGroup;
 use PKP\userGroup\relationships\UserGroupStage;
 use PKP\userGroup\UserGroup;
+use PKP\userGroup\Repository as UserGroupRepository;
+use Illuminate\Support\Facades\App;
 
 class NativeXmlUserGroupFilter extends \PKP\plugins\importexport\native\filter\NativeImportFilter
 {
@@ -70,45 +72,58 @@ public function handleElement($node)
         $context = $deployment->getContext();
 
         // Create the UserGroup object.
-        $userGroup = Repo::userGroup()->newDataObject();
-        $userGroup->setContextId($context->getId());
-
+        $userGroup = new UserGroup();
+        $userGroup->contextId = $context->getId();
+        
         // Extract the name node element to see if this user group exists already.
         $nodeList = $node->getElementsByTagNameNS($deployment->getNamespace(), 'name');
         if ($nodeList->length > 0) {
             $content = $this->parseLocalizedContent($nodeList->item(0)); // $content[1] contains the localized name.
-            $userGroups = Repo::userGroup()->getCollector()
-                ->filterByContextIds([$context->getId()])
-                ->getMany();
-
+            $userGroups = UserGroup::query()
+                ->withContextIds($context->getId())
+                ->get();
+        
             foreach ($userGroups as $testGroup) {
-                if (in_array($content[1], $testGroup->getName(null))) {
-                    return $testGroup;  // we found one with the same name.
+                if (in_array($content[1], $testGroup->name)) {
+                    return $testGroup;  // We found one with the same name.
                 }
             }
 
             for ($n = $node->firstChild; $n !== null; $n = $n->nextSibling) {
                 if ($n instanceof \DOMElement) {
                     switch ($n->tagName) {
-                        case 'role_id': $userGroup->setRoleId($n->textContent);
+                        case 'role_id':
+                            $userGroup->roleId = (int)$n->textContent;
                             break;
-                        case 'is_default': $userGroup->setDefault($n->textContent ?? false);
+                        case 'is_default':
+                            $userGroup->isDefault = filter_var($n->textContent, FILTER_VALIDATE_BOOLEAN);
                             break;
-                        case 'show_title': $userGroup->setShowTitle($n->textContent ?? true);
+                        case 'show_title':
+                            $userGroup->showTitle = filter_var($n->textContent, FILTER_VALIDATE_BOOLEAN, ['options' => ['default' => true]]);
                             break;
-                        case 'name': $userGroup->setName($n->textContent, $n->getAttribute('locale'));
+                        case 'name':
+                            $locale = $n->getAttribute('locale');
+                            $name = $userGroup->name ?? [];
+                            $name[$locale] = $n->textContent;
+                            $userGroup->name = $name;
                             break;
-                        case 'abbrev': $userGroup->setAbbrev($n->textContent, $n->getAttribute('locale'));
+                        case 'abbrev':
+                            $locale = $n->getAttribute('locale');
+                            $abbrev = $userGroup->abbrev ?? [];
+                            $abbrev[$locale] = $n->textContent;
+                            $userGroup->abbrev = $abbrev;
                             break;
-                        case 'permit_self_registration': $userGroup->setPermitSelfRegistration($n->textContent ?? false);
+                        case 'permit_self_registration':
+                            $userGroup->permitSelfRegistration = filter_var($n->textContent, FILTER_VALIDATE_BOOLEAN);
                             break;
-                        case 'permit_metadata_edit': $userGroup->setPermitMetadataEdit($n->textContent ?? false);
+                        case 'permit_metadata_edit':
+                            $userGroup->permitMetadataEdit = filter_var($n->textContent, FILTER_VALIDATE_BOOLEAN);
                             break;
                     }
                 }
             }
-
-            $userGroupId = Repo::userGroup()->add($userGroup);
+            $userGroup->save();
+            $userGroupId = $userGroup->id;
 
             $stageNodeList = $node->getElementsByTagNameNS($deployment->getNamespace(), 'stage_assignments');
             if ($stageNodeList->length == 1) {
diff --git a/plugins/importexport/users/filter/PKPUserUserXmlFilter.php b/plugins/importexport/users/filter/PKPUserUserXmlFilter.php
index e4725534866..809d5ee8bfd 100644
--- a/plugins/importexport/users/filter/PKPUserUserXmlFilter.php
+++ b/plugins/importexport/users/filter/PKPUserUserXmlFilter.php
@@ -23,6 +23,7 @@
 use PKP\plugins\importexport\native\filter\NativeExportFilter;
 use PKP\user\InterestManager;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 class PKPUserUserXmlFilter extends NativeExportFilter
 {
@@ -131,10 +132,9 @@ public function createPKPUserNode($doc, $user)
             $this->createOptionalNode($doc, $userNode, 'disabled_reason', $user->getDisabledReason());
         }
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByUserIds([$user->getId()])
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withUserIds([$user->getId()])
+            ->withContextIds([$context->getId()])
+            ->get();
 
         foreach ($userGroups as $userGroup) {
             $userNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'user_group_ref', htmlspecialchars($userGroup->getName($context->getPrimaryLocale()), ENT_COMPAT, 'UTF-8')));
@@ -154,9 +154,8 @@ public function addUserGroups($doc, $rootNode)
         $context = $deployment->getContext();
         $userGroupsNode = $doc->createElementNS($deployment->getNamespace(), 'user_groups');
 
-        $userGroups = Repo::userGroup()->getCollector()
-            ->filterByContextIds([$context->getId()])
-            ->getMany();
+        $userGroups = UserGroup::withContextIds([$context->getId()])
+        ->get();
 
         $filterDao = DAORegistry::getDAO('FilterDAO'); /** @var FilterDAO $filterDao */
         $userGroupExportFilters = $filterDao->getObjectsByGroup('usergroup=>user-xml');
diff --git a/plugins/importexport/users/filter/UserGroupNativeXmlFilter.php b/plugins/importexport/users/filter/UserGroupNativeXmlFilter.php
index eac5a815f4c..ec35792d241 100644
--- a/plugins/importexport/users/filter/UserGroupNativeXmlFilter.php
+++ b/plugins/importexport/users/filter/UserGroupNativeXmlFilter.php
@@ -82,17 +82,17 @@ public function createUserGroupNode($doc, $userGroup)
         $userGroupNode = $doc->createElementNS($deployment->getNamespace(), 'user_group');
 
         // Add metadata
-        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'role_id', $userGroup->getRoleId()));
-        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'context_id', $userGroup->getContextId()));
-        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'is_default', $userGroup->getDefault() ? 'true' : 'false'));
-        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'show_title', $userGroup->getShowTitle() ? 'true' : 'false'));
-        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'permit_self_registration', $userGroup->getPermitSelfRegistration() ? 'true' : 'false'));
-        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'permit_metadata_edit', $userGroup->getPermitMetadataEdit() ? 'true' : 'false'));
+        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'role_id', $userGroup->roleId));
+        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'context_id', $userGroup->contextId));
+        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'is_default', $userGroup->isDefault ? 'true' : 'false'));
+        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'show_title', $userGroup->showTitle ? 'true' : 'false'));
+        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'permit_selfRegistration', $userGroup->permitSelfRegistration ? 'true' : 'false'));
+        $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'permit_metadataEdit', $userGroup->permitMetadataEdit ? 'true' : 'false'));
 
-        $this->createLocalizedNodes($doc, $userGroupNode, 'name', $userGroup->getName(null));
-        $this->createLocalizedNodes($doc, $userGroupNode, 'abbrev', $userGroup->getAbbrev(null));
+        $this->createLocalizedNodes($doc, $userGroupNode, 'name', $userGroup->name);
+        $this->createLocalizedNodes($doc, $userGroupNode, 'abbrev', $userGroup->abbrev);
 
-        $assignedStages = Repo::userGroup()->getAssignedStagesByUserGroupId($context->getId(), $userGroup->getId())->toArray();
+        $assignedStages = $userGroup->getAssignedStageIds()->toArray();
 
         $userGroupNode->appendChild($doc->createElementNS($deployment->getNamespace(), 'stage_assignments', htmlspecialchars(join(':', $assignedStages), ENT_COMPAT, 'UTF-8')));
         return $userGroupNode;
diff --git a/plugins/importexport/users/filter/UserXmlPKPUserFilter.php b/plugins/importexport/users/filter/UserXmlPKPUserFilter.php
index 4f1599f0c91..37f17241d4f 100644
--- a/plugins/importexport/users/filter/UserXmlPKPUserFilter.php
+++ b/plugins/importexport/users/filter/UserXmlPKPUserFilter.php
@@ -28,6 +28,7 @@
 use PKP\site\SiteDAO;
 use PKP\user\InterestManager;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
 
 class UserXmlPKPUserFilter extends \PKP\plugins\importexport\native\filter\NativeImportFilter
 {
@@ -291,9 +292,8 @@ public function parseUser($node)
 
         // We can only assign a user to a user group if persisted to the database by $userId
         if ($userId) {
-            $userGroups = Repo::userGroup()->getCollector()
-                ->filterByContextIds([$context->getId()])
-                ->getMany();
+            $userGroups = UserGroup::withContextIds([$context->getId()])
+                ->get();
 
             // Extract user groups from the User XML and assign the user to those (existing) groups.
             // Note:  It is possible for a user to exist with no user group assignments so there is
@@ -307,9 +307,10 @@ public function parseUser($node)
                     foreach ($userGroups as $userGroup) {
                         // if the given user associated group name in within tag 'user_group_ref' is in the list of $userGroup name local list
                         // and the user is not already assigned to that group
-                        if (in_array($n->textContent, $userGroup->getName(null)) && !Repo::userGroup()->userInGroup($userId, $userGroup->getId())) {
+                        if (in_array($n->textContent, $userGroup->name) &&
+                            !UserGroup::userInGroup($userId, $userGroup->id)) {
                             // Found a candidate; assign user to it.
-                            Repo::userGroup()->assignUserToGroup($userId, $userGroup->getId());
+                            UserGroup::assignUserToGroup($userId, $userGroup->id);
                         }
                     }
                 }
diff --git a/schemas/userGroup.json b/schemas/userGroup.json
index ea266ea8553..bc98f009e13 100644
--- a/schemas/userGroup.json
+++ b/schemas/userGroup.json
@@ -2,59 +2,78 @@
 	"title": "UserGroup",
 	"description": "A user group assigned to one of the allowed roles.",
 	"properties": {
-		"abbrev": {
-			"type": "string",
-			"description": "The short name of the user group.",
-			"apiSummary": true,
-			"multilingual": true
-		},
-		"masthead": {
-			"type": "boolean"
-		},
-		"name": {
-			"type": "string",
-			"description": "The name of the user group.",
-			"apiSummary": true,
-			"multilingual": true
-		},
 		"id": {
-			"type": "integer",
-			"apiSummary": true
-		},
-		"contextId": {
-			"type": "integer",
-			"apiSummary": true
-		},
-		"permitSelfRegistration": {
-			"type": "boolean"
-		},
-		"permitMetadataEdit": {
-			"type": "boolean"
-		},
-		"recommendOnly": {
-			"type": "boolean"
-		},
-		"isDefault": {
-			"type": "boolean"
-		},
-		"roleId": {
-			"type": "integer",
-			"validation": [
-				"in:16,1,17,65536,4096,4097,1048576,209715"
-			]
-		},
-		"showTitle": {
-			"type": "boolean"
-		},
-		"nameLocaleKey": {
-			"type": "string",
-			"description": "A field that contains the the locale key of the group name",
-			"apiSummary": true
-		},
-		"abbrevLocaleKey": {
-			"type": "string",
-			"description": "A field that contains the the locale key of the group abbreviaton",
-			"apiSummary": true
-		}
-	}
+            "type": "integer",
+            "origin": "primary",
+            "apiSummary": true
+        },
+        "contextId": {
+            "type": "integer",
+            "origin": "primary",
+            "apiSummary": true
+        },
+        "roleId": {
+            "type": "integer",
+            "origin": "primary",
+            "validation": [
+                "in:16,1,17,65536,4096,4097,1048576,209715"
+            ]
+        },
+        "isDefault": {
+            "type": "boolean",
+            "origin": "primary"
+        },
+        "showTitle": {
+            "type": "boolean",
+            "origin": "primary"
+        },
+        "permitSelfRegistration": {
+            "type": "boolean",
+            "origin": "primary"
+        },
+        "permitMetadataEdit": {
+            "type": "boolean",
+            "origin": "primary"
+        },
+        "masthead": {
+            "type": "boolean",
+            "origin": "primary"
+        },
+        "name": {
+            "type": "string",
+            "origin": "setting",
+            "description": "The name of the user group.",
+            "apiSummary": true,
+            "multilingual": true
+        },
+        "namePlural": {
+            "type": "string",
+            "origin": "setting",
+            "description": "The plural name of the user group.",
+            "multilingual": true
+        },
+        "abbrev": {
+            "type": "string",
+            "origin": "setting",
+            "description": "The short name of the user group.",
+            "apiSummary": true,
+            "multilingual": true
+        },
+        "nameLocaleKey": {
+            "type": "string",
+            "origin": "setting",
+            "description": "The locale key of the group name.",
+            "apiSummary": true
+        },
+        "abbrevLocaleKey": {
+            "type": "string",
+            "origin": "setting",
+            "description": "The locale key of the group abbreviation.",
+            "apiSummary": true
+        },
+        "recommendOnly": {
+            "type": "boolean",
+            "origin": "setting"
+        }
+    }
 }
diff --git a/templates/controllers/grid/users/author/form/authorForm.tpl b/templates/controllers/grid/users/author/form/authorForm.tpl
index b8a7fa861d1..4463e79f704 100644
--- a/templates/controllers/grid/users/author/form/authorForm.tpl
+++ b/templates/controllers/grid/users/author/form/authorForm.tpl
@@ -46,8 +46,8 @@
 		{/if}
 		{fbvFormSection id="userGroupId" title="submission.submit.contributorRole" list=true required=true}
 			{foreach from=$authorUserGroups item=$userGroup}
-				{if $userGroupId == $userGroup->getId()}{assign var="checked" value=true}{else}{assign var="checked" value=false}{/if}
-				{fbvElement type="radio" id="userGroup"|concat:$userGroup->getId() name="userGroupId" value=$userGroup->getId() checked=$checked label=$userGroup->getLocalizedName() translate=false}
+				{if $userGroupId == $userGroup->id}{assign var="checked" value=true}{else}{assign var="checked" value=false}{/if}
+				{fbvElement type="radio" id="userGroup"|concat:$userGroup->id name="userGroupId" value=$userGroup->id checked=$checked label=$userGroup->getLocalizedData('name') translate=false}
 			{/foreach}
 		{/fbvFormSection}
 		{fbvFormSection list="true"}
diff --git a/templates/frontend/components/registrationFormContexts.tpl b/templates/frontend/components/registrationFormContexts.tpl
index cae256180e1..69b1bfeaf2d 100644
--- a/templates/frontend/components/registrationFormContexts.tpl
+++ b/templates/frontend/components/registrationFormContexts.tpl
@@ -41,11 +41,11 @@
 									{translate key="user.register.otherContextRoles"}
 								</legend>
 								{foreach from=$readerUserGroups[$contextId] item=userGroup}
-									{if $userGroup->getPermitSelfRegistration()}
-										{assign var="userGroupId" value=$userGroup->getId()}
+									{if $userGroup->permitSelfRegistration}
+										{assign var="userGroupId" value=$userGroup->id}
 										<label>
 											<input type="checkbox" name="readerGroup[{$userGroupId}]"{if in_array($userGroupId, $userGroupIds)} checked="checked"{/if}>
-											{$userGroup->getLocalizedName()}
+											{$userGroup->getLocalizedData('name')}
 										</label>
 										{if in_array($userGroupId, $userGroupIds)}
 											{assign var=isSelected value=true}
@@ -53,11 +53,11 @@
 									{/if}
 								{/foreach}
 								{foreach from=$reviewerUserGroups[$contextId] item=userGroup}
-									{if $userGroup->getPermitSelfRegistration()}
-										{assign var="userGroupId" value=$userGroup->getId()}
+									{if $userGroup->permitSelfRegistration}
+										{assign var="userGroupId" value=$userGroup->id}
 										<label>
 											<input type="checkbox" name="reviewerGroup[{$userGroupId}]"{if in_array($userGroupId, $userGroupIds)} checked="checked"{/if}>
-											{$userGroup->getLocalizedName()}
+											{$userGroup->getLocalizedData('name')}
 										</label>
 										{if in_array($userGroupId, $userGroupIds)}
 											{assign var=isSelected value=true}
diff --git a/templates/frontend/pages/userRegister.tpl b/templates/frontend/pages/userRegister.tpl
index 96525771865..973bf85c637 100644
--- a/templates/frontend/pages/userRegister.tpl
+++ b/templates/frontend/pages/userRegister.tpl
@@ -70,7 +70,7 @@
 			{assign var=contextId value=$currentContext->getId()}
 			{assign var=userCanRegisterReviewer value=0}
 			{foreach from=$reviewerUserGroups[$contextId] item=userGroup}
-				{if $userGroup->getPermitSelfRegistration()}
+				{if $userGroup->permitSelfRegistration}
 					{assign var=userCanRegisterReviewer value=$userCanRegisterReviewer+1}
 				{/if}
 			{/foreach}
@@ -87,11 +87,11 @@
 					<div class="fields">
 						<div id="reviewerOptinGroup" class="optin">
 							{foreach from=$reviewerUserGroups[$contextId] item=userGroup}
-								{if $userGroup->getPermitSelfRegistration()}
+								{if $userGroup->permitSelfRegistration}
 									<label>
-										{assign var="userGroupId" value=$userGroup->getId()}
+										{assign var="userGroupId" value=$userGroup->id}
 										<input type="checkbox" name="reviewerGroup[{$userGroupId}]" value="1"{if in_array($userGroupId, $userGroupIds)} checked="checked"{/if}>
-										{translate key=$checkboxLocaleKey userGroup=$userGroup->getLocalizedName()}
+										{translate key=$checkboxLocaleKey userGroup=$userGroup->getLocalizedData('name')}
 									</label>
 								{/if}
 							{/foreach}
diff --git a/templates/user/userGroupSelfRegistration.tpl b/templates/user/userGroupSelfRegistration.tpl
index 883533f4eeb..d1f480f17c0 100644
--- a/templates/user/userGroupSelfRegistration.tpl
+++ b/templates/user/userGroupSelfRegistration.tpl
@@ -11,35 +11,35 @@
  *}
 {assign var=contextId value=$context->getId()}
 {foreach from=$readerUserGroups[$contextId] item=userGroup}
-	{assign var="userGroupId" value=$userGroup->getId()}
-	{if in_array($userGroup->getId(), $userGroupIds)}
+	{assign var="userGroupId" value=$userGroup->id}
+	{if in_array($userGroup->id, $userGroupIds)}
 		{assign var="checked" value=true}
 	{else}
 		{assign var="checked" value=false}
 	{/if}
-	{if $userGroup->getPermitSelfRegistration()}
-		{fbvElement type="checkbox" id="readerGroup-$userGroupId" name="readerGroup[$userGroupId]" checked=$checked label=$userGroup->getLocalizedName()|escape translate=false}
+	{if $userGroup->permitSelfRegistration}
+		{fbvElement type="checkbox" id="readerGroup-$userGroupId" name="readerGroup[$userGroupId]" checked=$checked label=$userGroup->getLocalizedData('name')|escape translate=false}
 	{/if}
 {/foreach}
 {foreach from=$authorUserGroups[$contextId] item=userGroup}
-	{assign var="userGroupId" value=$userGroup->getId()}
-	{if in_array($userGroup->getId(), $userGroupIds)}
+	{assign var="userGroupId" value=$userGroup->id}
+	{if in_array($userGroup->id, $userGroupIds)}
 		{assign var="checked" value=true}
 	{else}
 		{assign var="checked" value=false}
 	{/if}
-	{if $userGroup->getPermitSelfRegistration()}
-		{fbvElement type="checkbox" id="authorGroup-$userGroupId" name="authorGroup[$userGroupId]" checked=$checked label=$userGroup->getLocalizedName()|escape translate=false}
+	{if $userGroup->permitSelfRegistration}
+		{fbvElement type="checkbox" id="authorGroup-$userGroupId" name="authorGroup[$userGroupId]" checked=$checked label=$userGroup->getLocalizedData('name')|escape translate=false}
 	{/if}
 {/foreach}
 {foreach from=$reviewerUserGroups[$contextId] item=userGroup}
-	{assign var="userGroupId" value=$userGroup->getId()}
-	{if in_array($userGroup->getId(), $userGroupIds)}
+	{assign var="userGroupId" value=$userGroup->id}
+	{if in_array($userGroup->id, $userGroupIds)}
 		{assign var="checked" value=true}
 	{else}
 		{assign var="checked" value=false}
 	{/if}
-	{if $userGroup->getPermitSelfRegistration()}
-		{fbvElement type="checkbox" id="reviewerGroup-$userGroupId" name="reviewerGroup[$userGroupId]" checked=$checked label=$userGroup->getLocalizedName()|escape translate=false}
+	{if $userGroup->permitSelfRegistration}
+		{fbvElement type="checkbox" id="reviewerGroup-$userGroupId" name="reviewerGroup[$userGroupId]" checked=$checked label=$userGroup->getLocalizedData('name')|escape translate=false}
 	{/if}
 {/foreach}
diff --git a/tests/classes/security/authorization/PolicyTestCase.php b/tests/classes/security/authorization/PolicyTestCase.php
index 25652d2a891..2c41129a609 100644
--- a/tests/classes/security/authorization/PolicyTestCase.php
+++ b/tests/classes/security/authorization/PolicyTestCase.php
@@ -32,6 +32,8 @@
 use PKP\security\Role;
 use PKP\tests\PKPTestCase;
 use PKP\user\User;
+use PKP\userGroup\UserGroup;
+
 
 abstract class PolicyTestCase extends PKPTestCase
 {
@@ -103,8 +105,8 @@ public function mockEffect()
         // Add a user group to the authorized context
         // of the authorization context manipulation policy.
         $policy = $this->getAuthorizationContextManipulationPolicy();
-        $userGroup = Repo::userGroup()->newDataObject();
-        $userGroup->setRoleId(self::ROLE_ID_TEST);
+        $userGroup = new UserGroup();
+        $userGroup->roleId = self::ROLE_ID_TEST;
         $policy->addAuthorizedContextObject(Application::ASSOC_TYPE_USER_GROUP, $userGroup);
 
         // Add user roles array to the authorized context.