For me it seems that Windows 2020-11 Cumulative Update has solved the problem.
I was able to update a VM installation that has failed before on both ways:
- Installing the 2020-11 updates on Windows 10 Version 2004 and updating to Windows 20H2 with installed Avast Free Antivirus
- Removing Avast and updating to Windows 20H2, then installing the 2020-11 Cumulative Update and reinistalling Avast afterwards
Though I wouldn't go any risk and won't make the update without a reliable backup/restore path
This solution was perfect for me. I had to reinstall windows 2 times. After upgrading to windows version 20H2 I tried to install avast and it gave a fatal error and windows did not recover.
After seeing this comment I did the procedure of installing windows 20H2, installing "Windows 2020-11 Cumulative Update" and then avast. Worked perfectly. There should be a warning on the avast website or something regarding the need for this update.
Thanks for sharing this info.