I reproduced the problem with the above file. I replaced one line with the following, and haven't reproduced the problem for 24 hours since:
Option "AccelMethod" "uxa" -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1921595 Title: Screen flickers in Ubuntu Mate 21.04 and Ubuntu Unity 21.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1921595/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
