build-aux,CI: Replace Flatpak KDE SDK with Freedesktop SDK

The Qt components are from the same repo as other dependencies.

The KDE Platform was never a good fit for OBS Studio for multiple
reasons:
- Life cycle too short and misaligned with OBS Studio causing users to
  get EOL notification too often.
- Third-party Qt plugins were allowed which could change Qt's behavior.
- KDE exclusives sandboxed holes were inherited.

.github/workflows/build-project.yaml

@@ -249,7 +249,7 @@ jobs:
     env:
       FLATPAK_BUILD_SHARE_PATH: flatpak_app/files/share
     container:
-      image: ghcr.io/flathub-infra/flatpak-github-actions:kde-6.8
+      image: ghcr.io/flathub-infra/flatpak-github-actions:freedesktop-24.08
       options: --privileged
       volumes:
         - /usr/local/lib/android:/to_clean/android

.github/workflows/publish.yaml

@@ -87,7 +87,7 @@ jobs:
       YOUTUBE_SECRET: ${{ secrets.YOUTUBE_SECRET }}
       YOUTUBE_SECRET_HASH: ${{ secrets.YOUTUBE_SECRET_HASH }}
     container:
-      image: ghcr.io/flathub-infra/flatpak-github-actions:kde-6.8
+      image: ghcr.io/flathub-infra/flatpak-github-actions:freedesktop-24.08
       options: --privileged
       volumes:
         - /usr/local/lib/android:/to_clean/android

build-aux/com.obsproject.Studio.json

@@ -1,8 +1,8 @@
 {
     "id": "com.obsproject.Studio",
-    "runtime": "org.kde.Platform",
-    "runtime-version": "6.8",
-    "sdk": "org.kde.Sdk",
+    "runtime": "org.freedesktop.Platform",
+    "runtime-version": "24.08",
+    "sdk": "org.freedesktop.Sdk",
     "command": "obs",
     "finish-args": [
         "--socket=wayland",
@@ -86,6 +86,21 @@
                 }
             ]
         },
+        {
+            "name": "qt",
+            "buildsystem": "simple",
+            "build-commands": [
+                "tar -xvf qt.tar.xz -C /"
+            ],
+            "sources": [
+                {
+                    "type": "file",
+                    "dest-filename": "qt.tar.xz",
+                    "url": "https://github.com/obsproject/obs-deps-buildstream/releases/download/2025-10-03/flatpak-qt-x86_64-2025-10-03.tar.xz",
+                    "sha256": "79d7377da42e1eea2a18ed76407c1db716a80778fe34ef1f68b9eb7ca6d89cbf"
+                }
+            ]
+        },
         {
             "name": "cef",
             "build-options": {