I think I followed your steps now.
1 Uninstall with DDU
2 Reboot into Safe Mode
3 Start the installer -> same error
3.1 Manual install via Device Manager
4. Reboot
5. Test
-> Seems good
-> Testing with browser and googled sth
-> Tab crashed
-> Testing with a news site
-> Tab crashed
-> soon after browser crashed
-> Testing with Windows Store
-> Crashed in about a minute
-- No Desktop Manager crashes - they have returned after some time
NB: there are some Windows Updates. And I did not run the GUI installer again after manual install. Made another MTB
1 Uninstall with DDU
2 Reboot into Safe Mode
3 Start the installer -> same error
3.1 Manual install via Device Manager
4. Reboot
5. Test
-> Seems good
-> Testing with browser and googled sth
-> Tab crashed
-> Testing with a news site
-> Tab crashed
-> soon after browser crashed
-> Testing with Windows Store
-> Crashed in about a minute
-- No Desktop Manager crashes - they have returned after some time
NB: there are some Windows Updates. And I did not run the GUI installer again after manual install. Made another MTB