I used the hirsute LiveCD again and it has mesa 21.0.1.
I refreshed apt but there wasn't any update of mesa. So I enabled hirsute-proposed and upgraded mesa to 21.0.3.
Then I logged out and straight away there were glitches on the login screen. I've logged in and confirmed that Gnome Shell and programs now also have graphical glitches.
Then I used the ppa and it solved the problem. So I confirm that the fix works.
I used the hirsute LiveCD again and it has mesa 21.0.1.
I refreshed apt but there wasn't any update of mesa. So I enabled hirsute-proposed and upgraded mesa to 21.0.3.
Then I logged out and straight away there were glitches on the login screen. I've logged in and confirmed that Gnome Shell and programs now also have graphical glitches.
Then I used the ppa and it solved the problem. So I confirm that the fix works.