Have you tried using different proton versions wit hit? Launcher uses .NET/C# so it can be problematic. After the first execution you should be able to just add --launcher-skip
to the command and skip it.
Execute steam with PRESSURE_VESSEL_SHELL=instead steam and launch the game. In the term it will open type "$@"
(with the ") and paste output here, we'll see what proton fusses about