This bug is closed because it was fixed, so you're seeing a different problem. Please file a new bug. Flatpak could be a factor here, note above there is another bug linked were specific fixes were needed for Snap too.
Edit: Your log shows VA-API successfully initializing, so this looks unrelated to RDD/sandboxing and may be a completely unrelated performance thing. Again, file a new bug specific to your problem.
This bug is closed because it was fixed, so you're seeing a different problem. Please file a new bug. Flatpak could be a factor here, note above there is another bug linked were specific fixes were needed for Snap too.
Edit: Your log shows VA-API successfully initializing, so this looks unrelated to RDD/sandboxing and may be a completely unrelated performance thing. Again, file a new bug specific to your problem.