diff --git a/pkgs/development/cuda-modules/cuda-library-samples/generic.nix b/pkgs/development/cuda-modules/cuda-library-samples/generic.nix
index f5d1c250cfca..43d2bece88c9 100644
--- a/pkgs/development/cuda-modules/cuda-library-samples/generic.nix
+++ b/pkgs/development/cuda-modules/cuda-library-samples/generic.nix
@@ -36,6 +36,7 @@ let
         cuSPARSE, cuSOLVER, cuFFT, cuRAND, NPP and nvJPEG.
       '';
       license = lib.licenses.bsd3;
+      platforms = [ "x86_64-linux" ];
       maintainers = with lib.maintainers; [ obsidian-systems-maintenance ] ++ lib.teams.cuda.members;
     };
   };
diff --git a/pkgs/development/cuda-modules/cuda-samples/generic.nix b/pkgs/development/cuda-modules/cuda-samples/generic.nix
index ed9c57f3d00c..97e05957d3ed 100644
--- a/pkgs/development/cuda-modules/cuda-samples/generic.nix
+++ b/pkgs/development/cuda-modules/cuda-samples/generic.nix
@@ -73,6 +73,7 @@ backendStdenv.mkDerivation (finalAttrs: {
     description = "Samples for CUDA Developers which demonstrates features in CUDA Toolkit";
     # CUDA itself is proprietary, but these sample apps are not.
     license = lib.licenses.bsd3;
+    platforms = [ "x86_64-linux" ];
     maintainers = with lib.maintainers; [ obsidian-systems-maintenance ] ++ lib.teams.cuda.members;
   };
 })
diff --git a/pkgs/test/build-environment-info/default.nix b/pkgs/test/build-environment-info/default.nix
index f0c71d8d1eaf..dce91edbf4d1 100644
--- a/pkgs/test/build-environment-info/default.nix
+++ b/pkgs/test/build-environment-info/default.nix
@@ -1,11 +1,39 @@
-{ runCommand }:
+{
+  lib,
+  stdenv,
+  runCommand,
+  getent,
+  xcbuild,
+}:
 
 # Prints information about the state of the build environment for
 # assistance debugging Hydra. Feel free to add anything you would find
 # useful to this.
-runCommand "build-environment-info" { } ''
-  ulimit -a
+runCommand "build-environment-info"
+  {
+    nativeBuildInputs = [ getent ] ++ lib.optionals stdenv.buildPlatform.isDarwin [ xcbuild ];
+  }
+  ''
+    # It’s useful to get more info even if a command fails.
+    set +e
 
-  # Always fail so that this job can easily be restarted.
-  exit 1
-''
+    run() {
+      echoCmd : "$@"
+      "$@"
+    }
+
+    run uname -a
+
+    ${lib.optionalString stdenv.buildPlatform.isDarwin ''
+      run env SYSTEM_VERSION_COMPAT=0 plutil -p /System/Library/CoreServices/SystemVersion.plist
+    ''}
+
+    run id
+
+    run getent passwd "$(id -un)"
+
+    run ulimit -a
+
+    # Always fail so that this job can easily be restarted.
+    run exit 1
+  ''
diff --git a/pkgs/test/nixos-functions/default.nix b/pkgs/test/nixos-functions/default.nix
index bdd5e3c6d8b4..fc9a726570ff 100644
--- a/pkgs/test/nixos-functions/default.nix
+++ b/pkgs/test/nixos-functions/default.nix
@@ -17,15 +17,13 @@ let
     versionSuffix = "test";
     label = "test";
   };
-in lib.optionalAttrs stdenv.hostPlatform.isLinux (
-  pkgs.recurseIntoAttrs {
+in pkgs.recurseIntoAttrs {
 
-    nixos-test = (pkgs.nixos {
-      system.nixos = dummyVersioning;
-      boot.loader.grub.enable = false;
-      fileSystems."/".device = "/dev/null";
-      system.stateVersion = lib.trivial.release;
-    }).toplevel;
+  nixos-test = (pkgs.nixos {
+    system.nixos = dummyVersioning;
+    boot.loader.grub.enable = false;
+    fileSystems."/".device = "/dev/null";
+    system.stateVersion = lib.trivial.release;
+  }).toplevel;
 
-  }
-)
+}
diff --git a/pkgs/tools/typesetting/tex/texlive/build-texlive-package.nix b/pkgs/tools/typesetting/tex/texlive/build-texlive-package.nix
index 1356fc325047..ac4375c1960d 100644
--- a/pkgs/tools/typesetting/tex/texlive/build-texlive-package.nix
+++ b/pkgs/tools/typesetting/tex/texlive/build-texlive-package.nix
@@ -66,6 +66,11 @@ let
     '';
     # discourage nix-env from matching this package
     priority = 10;
+    platforms = lib.platforms.all;
+    # These create a large number of jobs, which puts load on Hydra
+    # without any appreciable benefit (as the combined packages already
+    # cause them all to be built and cached anyway).
+    hydraPlatforms = [ ];
   } // lib.optionalAttrs (args ? shortdesc) {
     description = args.shortdesc;
   };
diff --git a/pkgs/top-level/php-packages.nix b/pkgs/top-level/php-packages.nix
index 7665c2ff4b58..0d864e837ff2 100644
--- a/pkgs/top-level/php-packages.nix
+++ b/pkgs/top-level/php-packages.nix
@@ -181,8 +181,8 @@ in {
 
       meta = {
         description = "PHP upstream extension: ${name}";
-        inherit (php.meta) maintainers homepage license;
-      };
+        inherit (php.meta) maintainers homepage license platforms;
+      } // args.meta or { };
     }));
 
   php = phpPackage;
@@ -461,13 +461,6 @@ in {
           env = lib.optionalAttrs stdenv.hostPlatform.isDarwin { NIX_LDFLAGS = "-liconv"; };
           doCheck = stdenv.hostPlatform.isLinux;
         }
-        {
-          name = "imap";
-          buildInputs = [ uwimap openssl pam pcre2 libkrb5 ];
-          configureFlags = [ "--with-imap=${uwimap}" "--with-imap-ssl" "--with-kerberos" ];
-          # Using version from PECL on new PHP versions.
-          enable = lib.versionOlder php.version "8.3";
-        }
         {
           name = "intl";
           buildInputs = [ icu73 ];
@@ -563,7 +556,7 @@ in {
           internalDeps = [ php.extensions.pdo ];
           configureFlags = [ "--with-pdo-dblib=${freetds}" ];
           # Doesn't seem to work on darwin.
-          enable = (!stdenv.hostPlatform.isDarwin);
+          meta.broken = (!stdenv.hostPlatform.isDarwin);
           doCheck = false;
         }
         {
@@ -658,7 +651,7 @@ in {
           buildInputs = [ net-snmp openssl ];
           configureFlags = [ "--with-snmp" ];
           # net-snmp doesn't build on darwin.
-          enable = (!stdenv.hostPlatform.isDarwin);
+          meta.broken = (!stdenv.hostPlatform.isDarwin);
           doCheck = false;
         }
         {
@@ -813,6 +806,13 @@ in {
             "--with-zlib"
           ];
         }
+      ] ++ lib.optionals (lib.versionOlder php.version "8.3") [
+        # Using version from PECL on new PHP versions.
+        {
+          name = "imap";
+          buildInputs = [ uwimap openssl pam pcre2 libkrb5 ];
+          configureFlags = [ "--with-imap=${uwimap}" "--with-imap-ssl" "--with-kerberos" ];
+        }
       ];
 
       # Convert the list of attrs:
@@ -821,14 +821,12 @@ in {
       # [ { name = <name>; value = <extension drv>; } ... ]
       #
       # which we later use listToAttrs to make all attrs available by name.
-      #
-      # Also filter out extensions based on the enable property.
       namedExtensions = builtins.map
         (drv: {
           name = drv.name;
-          value = mkExtension (builtins.removeAttrs drv [ "enable" ]);
+          value = mkExtension drv;
         })
-        (builtins.filter (i: i.enable or true) extensionData);
+        extensionData;
 
       # Produce the final attribute set of all extensions defined.
     in
diff --git a/pkgs/top-level/release-lib.nix b/pkgs/top-level/release-lib.nix
index e27b65dbd49a..41221f8b89f3 100644
--- a/pkgs/top-level/release-lib.nix
+++ b/pkgs/top-level/release-lib.nix
@@ -169,7 +169,7 @@ let
       if isDerivation value then
         value.meta.hydraPlatforms
           or (subtractLists (value.meta.badPlatforms or [])
-               (value.meta.platforms or [ "x86_64-linux" ]))
+               (value.meta.platforms or supportedSystems))
       else if value.recurseForDerivations or false || value.recurseForRelease or false then
         packagePlatforms value
       else