I saw somebody posting this a few days ago.

I clicked the link they posted, it was just an statement saying that it wasn’t officially supported on linux or MacOS, but it didn’t have a date.

I think the person just saw the text and thought it was recent, but the native support for linux was dropped a long time ago. We just use proton now like we normally do on other games.

Did exactly that. Looks like it was a problem with Proton 9.0-4, changed to 8.0-5 (after uninstalling every proton version and resinstalling the game)

Many thanks! I uninstalled all proton versions I had installed on steam.

I then redownloaded the game (the most painful part) and tried the Proton Experimental, which caused an error saying the compatibility tool failed. I then tried the Proton 8.0-5 (since I was using the 9.0-4 previously) and the problem went away.