Removed the package for this extensions and also the extensions in that directory. After that I logout and login again and started the game Portal two times, one using GameMode and the other not using it. Both times the game couldn't go full screen correctly.
** Changed in: mutter (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to mutter in Ubuntu. https://bugs.launchpad.net/bugs/1905637 Title: Games don't go full screen correctly with newer version of libmutter To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1905637/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs