I had to fiddle with proton a lot. Got the GE-build that was suggested by other users. The dotnet installation failed when I tried from the command line. I let steam handle it by just launching from the library. Then I got a never ending protonfixes dialog. I killed that, launched again. That got me into the settings menu. Then killed it again, launched again and was able to play!

Final touch was to use protontricks to install allfonts. That took care of missing fonts in the menu.