https://www.bleepingcomputer.com/news/microsoft/windows-11-incompatible-with-apps-using-non-ascii-registry-keys/

Microsoft is blocking Windows 11 upgrades if customers use applications that create registry keys using some non-ASCII characters.

As the company explains, on impacted systems such apps might be unable to open and could also cause other issues or errors in Windows 11, version 21H2 including blue screens.