I nuked NixOS so can’t really test but doubt this is relevant. It was working before and Arch has the same issue.

Weirdly, anything after Proton 8 was not able to properly recreate the compatdata folder because of a bug in the script. I fixed the bug and get it to generate the prefix but the issue with the game not launching is still there.

545 was working until recently

Okay, will give it a try. We’re talking about SteamLibrary/steamapps/compatdata/<gameid> right?

I have reinstalled the games. Does steam preserve compatdata if you uninstall a game?