linux: Detect unofficial Flatpaks

This is a quick and dirty detection that assumes that if a distribution
were to package their own Flatpak, they would also use their own custom
built runtime (we already have one such example).

A "proper" detection would involve changing how and what OBS logs about
the Flatpak environment and use that instead. Since that requires some
additional considerations, that is out of scope for now.

checks/linux.py

@@ -58,7 +58,11 @@ def checkDistro(lines):
 def checkFlatpak(lines):
     isFlatpak = search('Flatpak Runtime:', lines)
 
-    if len(isFlatpak) > 0:
+    if isFlatpak and ('org.kde.Platform' not in isFlatpak[0]) and ('org.freedesktop.Platform' not in isFlatpak[0]):
+        return [LEVEL_WARNING, "Unofficial Flatpak",
+                "You are using an unofficial Flatpak package. Please file issues with the packager.<br><br>OBS may be unable to assist with issues arising out of the usage of this package. We recommend following our <a href=\"https://obsproject.com/download#linux\">Install Instructions</a> instead."]
+
+    if isFlatpak:
         return [LEVEL_INFO, "Flatpak",
                 "You are using the Flatpak. Plugins are available as Flatpak extensions, which you can find in your Distribution's Software Center or via <code>flatpak search com.obsproject.Studio</code>. Installation of external plugins is not supported."]