diff --git a/backport-changelog/6.8/8123.md b/backport-changelog/6.8/8123.md
new file mode 100644
index 00000000000000..bfb291a55f15e9
--- /dev/null
+++ b/backport-changelog/6.8/8123.md
@@ -0,0 +1,3 @@
+https://github.com/WordPress/wordpress-develop/pull/8123
+
+* https://github.com/WordPress/gutenberg/pull/68549
diff --git a/lib/compat/wordpress-6.8/class-gutenberg-rest-post-types-controller-6-8.php b/lib/compat/wordpress-6.8/class-gutenberg-rest-post-types-controller-6-8.php
deleted file mode 100644
index da0489210e21f1..00000000000000
--- a/lib/compat/wordpress-6.8/class-gutenberg-rest-post-types-controller-6-8.php
+++ /dev/null
@@ -1,61 +0,0 @@
-<?php
-/**
- * REST API: Gutenberg_REST_Post_Types_Controller_6_8 class
- *
- * @package gutenberg
- */
-
-/**
- * Gutenberg_REST_Post_Types_Controller_6_8 class
- *
- * Add Block Editor default rendering mode to the post type response
- * to allow enabling/disabling at the post type level.
- */
-class Gutenberg_REST_Post_Types_Controller_6_8 extends WP_REST_Post_Types_Controller {
-	/**
-	 * Add Block Editor default rendering mode setting to the response.
-	 *
-	 * @param  WP_Post_Type    $item    Post type object.
-	 * @param  WP_REST_Request $request Request object.
-	 * @return WP_REST_Response Response object.
-	 */
-	public function prepare_item_for_response( $item, $request ) {
-		$response = parent::prepare_item_for_response( $item, $request );
-		$context  = ! empty( $request['context'] ) ? $request['context'] : 'view';
-
-		// Property will only exist if the post type supports the block editor.
-		if ( 'edit' === $context && property_exists( $item, 'default_rendering_mode' ) ) {
-			/**
-			 * Filters the block editor rendering mode for a post type.
-			 *
-			 * @since 6.8.0
-			 * @param string       $default_rendering_mode Default rendering mode for the post type.
-			 * @param WP_Post_Type $post_type              Post type name.
-			 * @return string Default rendering mode for the post type.
-			 */
-			$rendering_mode = apply_filters( 'post_type_default_rendering_mode', $item->default_rendering_mode, $item );
-
-			/**
-			 * Filters the block editor rendering mode for a specific post type.
-			 * Applied after the generic `post_type_default_rendering_mode` filter.
-			 *
-			 * The dynamic portion of the hook name, `$item->name`, refers to the post type slug.
-			 *
-			 * @since 6.8.0
-			 * @param string       $default_rendering_mode Default rendering mode for the post type.
-			 * @param WP_Post_Type $post_type              Post type object.
-			 * @return string Default rendering mode for the post type.
-			 */
-			$rendering_mode = apply_filters( "post_type_{$item->name}_default_rendering_mode", $rendering_mode, $item );
-
-			// Validate the filtered rendering mode.
-			if ( ! in_array( $rendering_mode, gutenberg_post_type_rendering_modes(), true ) ) {
-				$rendering_mode = 'post-only';
-			}
-
-			$response->data['default_rendering_mode'] = $rendering_mode;
-		}
-
-		return rest_ensure_response( $response );
-	}
-}
diff --git a/lib/compat/wordpress-6.8/post.php b/lib/compat/wordpress-6.8/post.php
index be842d89b51519..50324766488992 100644
--- a/lib/compat/wordpress-6.8/post.php
+++ b/lib/compat/wordpress-6.8/post.php
@@ -1,60 +1,26 @@
 <?php
-/**
- * Temporary compatibility shims for block APIs present in Gutenberg.
- *
- * @package gutenberg
- */
 
 /**
- * Get the available rendering modes for the Block Editor.
+ * Set the default editor mode for the page post type to `template-locked`.
  *
- * post-only: This mode extracts the post blocks from the template and renders only those.
- * The idea is to allow the user to edit the post/page in isolation without the wrapping template.
+ * Note: This backports into `create_initial_post_types` in WordPress Core.
  *
- * template-locked: This mode renders both the template and the post blocks
- * but the template blocks are locked and can't be edited. The post blocks are editable.
- *
- * @return array Array of available rendering modes.
- */
-function gutenberg_post_type_rendering_modes() {
-	return array(
-		'post-only',
-		'template-locked',
-	);
-}
-
-/**
- * Add the default_rendering_mode property to the WP_Post_Type object.
- * This property can be overwritten by using the post_type_default_rendering_mode filter.
- *
- * @param array  $args      Array of post type arguments.
- * @param string $post_type Post type key.
+ * @param array $args Array of post type arguments.
  * @return array Updated array of post type arguments.
  */
-function gutenberg_post_type_default_rendering_mode( $args, $post_type ) {
-	if ( ! wp_is_block_theme() || ! current_theme_supports( 'block-templates' ) ) {
+function gutenberg_update_page_editor_support( $args ) {
+	if ( empty( $args['supports'] ) ) {
 		return $args;
 	}
 
-	// Make sure the post type supports the block editor.
-	if (
-		( isset( $args['show_in_rest'] ) && $args['show_in_rest'] ) &&
-		( ! empty( $args['supports'] ) && in_array( 'editor', $args['supports'], true ) )
-	) {
-		$rendering_mode  = 'page' === $post_type ? 'template-locked' : 'post-only';
-		$rendering_modes = gutenberg_post_type_rendering_modes();
-
-		// Validate the supplied rendering mode.
-		if (
-			isset( $args['default_rendering_mode'] ) &&
-			in_array( $args['default_rendering_mode'], $rendering_modes, true )
-		) {
-			$rendering_mode = $args['default_rendering_mode'];
-		}
-
-		$args['default_rendering_mode'] = $rendering_mode;
+	$editor_support_key = array_search( 'editor', $args['supports'], true );
+	if ( false !== $editor_support_key ) {
+		unset( $args['supports'][ $editor_support_key ] );
+		$args['supports']['editor'] = array(
+			'default_mode' => 'template-locked',
+		);
 	}
 
 	return $args;
 }
-add_filter( 'register_post_type_args', 'gutenberg_post_type_default_rendering_mode', 10, 2 );
+add_action( 'register_page_post_type_args', 'gutenberg_update_page_editor_support' );
diff --git a/lib/compat/wordpress-6.8/rest-api.php b/lib/compat/wordpress-6.8/rest-api.php
index b94e42d5f2ccd0..cc3d3e89014e93 100644
--- a/lib/compat/wordpress-6.8/rest-api.php
+++ b/lib/compat/wordpress-6.8/rest-api.php
@@ -6,21 +6,6 @@
  * @package gutenberg
  */
 
-if ( ! defined( 'ABSPATH' ) ) {
-	die( 'Silence is golden.' );
-}
-
-if ( ! function_exists( 'gutenberg_add_post_type_rendering_mode' ) ) {
-	/**
-	 * Add Block Editor default rendering mode to the post type response.
-	 */
-	function gutenberg_add_post_type_rendering_mode() {
-		$controller = new Gutenberg_REST_Post_Types_Controller_6_8();
-		$controller->register_routes();
-	}
-}
-add_action( 'rest_api_init', 'gutenberg_add_post_type_rendering_mode' );
-
 // When querying terms for a given taxonomy in the REST API, respect the default
 // query arguments set for that taxonomy upon registration.
 function gutenberg_respect_taxonomy_default_args_in_rest_api( $args ) {
diff --git a/lib/load.php b/lib/load.php
index 371f9c54e5fc4a..69ba59e3718842 100644
--- a/lib/load.php
+++ b/lib/load.php
@@ -44,7 +44,6 @@ function gutenberg_is_experiment_enabled( $name ) {
 	// WordPress 6.8 compat.
 	require __DIR__ . '/compat/wordpress-6.8/block-comments.php';
 	require __DIR__ . '/compat/wordpress-6.8/class-gutenberg-rest-comment-controller-6-8.php';
-	require __DIR__ . '/compat/wordpress-6.8/class-gutenberg-rest-post-types-controller-6-8.php';
 	require __DIR__ . '/compat/wordpress-6.8/class-gutenberg-hierarchical-sort.php';
 	require __DIR__ . '/compat/wordpress-6.8/rest-api.php';
 
diff --git a/packages/editor/src/components/provider/index.js b/packages/editor/src/components/provider/index.js
index 133a52e2ce01bc..81435d966b44e4 100644
--- a/packages/editor/src/components/provider/index.js
+++ b/packages/editor/src/components/provider/index.js
@@ -56,6 +56,11 @@ const NON_CONTEXTUAL_POST_TYPES = [
 	'wp_template_part',
 ];
 
+/**
+ * These are rendering modes that the editor supports.
+ */
+const RENDERING_MODES = [ 'post-only', 'template-locked' ];
+
 /**
  * Depending on the post, template and template mode,
  * returns the appropriate blocks and change handlers for the block editor provider.
@@ -171,7 +176,6 @@ export const ExperimentalEditorProvider = withRegistryProvider(
 			mode,
 			defaultMode,
 			postTypeEntities,
-			hasLoadedPostObject,
 		} = useSelect(
 			( select ) => {
 				const {
@@ -180,24 +184,32 @@ export const ExperimentalEditorProvider = withRegistryProvider(
 					getRenderingMode,
 					__unstableIsEditorReady,
 				} = select( editorStore );
-				const { getEntitiesConfig } = select( coreStore );
+				const {
+					getEntitiesConfig,
+					getPostType,
+					hasFinishedResolution,
+				} = select( coreStore );
 
-				const postTypeObject = select( coreStore ).getPostType(
-					post.type
+				const postTypeSupports = getPostType( post.type )?.supports;
+				const hasLoadedPostObject = hasFinishedResolution(
+					'getPostType',
+					[ post.type ]
 				);
 
-				const _hasLoadedPostObject = select(
-					coreStore
-				).hasFinishedResolution( 'getPostType', [ post.type ] );
+				const _defaultMode = Array.isArray( postTypeSupports?.editor )
+					? postTypeSupports.editor.find(
+							( features ) => 'default_mode' in features
+					  )?.default_mode
+					: undefined;
+				const hasDefaultMode = RENDERING_MODES.includes( _defaultMode );
 
 				return {
-					hasLoadedPostObject: _hasLoadedPostObject,
 					editorSettings: getEditorSettings(),
-					isReady: __unstableIsEditorReady(),
+					isReady: __unstableIsEditorReady() && hasLoadedPostObject,
 					mode: getRenderingMode(),
 					defaultMode:
-						hasTemplate && postTypeObject?.default_rendering_mode
-							? postTypeObject?.default_rendering_mode
+						hasTemplate && hasDefaultMode
+							? _defaultMode
 							: 'post-only',
 					selection: getEditorSelection(),
 					postTypeEntities:
@@ -334,7 +346,7 @@ export const ExperimentalEditorProvider = withRegistryProvider(
 		// Register the editor commands.
 		useCommands();
 
-		if ( ! isReady || ! mode || ! hasLoadedPostObject ) {
+		if ( ! isReady || ! mode ) {
 			return null;
 		}