I was able to solve my problem from yesterday, now Teams starts without any problems
(C:\Users\%USERNAME%\AppData\Local\Publishers\8wekyb3d8bbwe\TeamsSharedConfig\* and C:\Users\%USERNAME%\AppData\Local\Packages\MSTeams_8wekyb3d8bbwe\* deleted).
Unfortunately, I now have a new problem with Hotfix 4 (I don't have the problem with Hotfix 3). Teams does not save any settings.
Reason: The folder C:\Users\%USERNAME%\AppData\Local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\ is missing. As a result, the file C:\Users\%USERNAME%\AppData\Local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams\app_settings.json is also missing.
If I delete my FSLogix profile and a new, empty one is created, same behaviour, app_settings.json is missing.
If I stop the FSLogix services and create a new, local profile, the app_settings.json file is created and Teams saves changes.
Does anyone else have this problem, does anyone know a solution?