If you have set up Steam “Family Library Sharing” in Ubuntu (Or other.) Linux (Perhaps following https://blog.budhajeewa.com/make-steam-family-library-sharing-effective-in-ubuntu-linux/.), you will notice that Windows games running with Steam Proton are not working when the secondary user (The one who is borrowing the games.) is trying to play them.
To fix this, log in to the secondary user’s Ubuntu account, and exit Steam completely (By clicking on the Steam icon in the notification area and selecting “Exit Steam”) and launch Steam again through a terminal.
This will allows us to see a bunch of output emitted from the running Steam application.
Once you are in Steam application, navigate to the game that doesn’t work, and click on “Play”. Now keep an eye on the messages that pop-up in the terminal. When the game crashes, you might see a message like this:
wineserver: /share/SteamLibrary/steamapps/compatdata/XXXXXXX/pfx is not owned by you wine: '/share/SteamLibrary/steamapps/compatdata/XXXXXXXpfx' is not owned by you
XXXXXXX would be a random number. Be sure that use the exact path that you get.
This is Steam complaining that the current Ubuntu user doesn’t have access to the above directory path. That is because it is owned by the user who installed the game. To let the secondary user play the game, we have to change the ownership of that directory to the secondary user.
sudo chown -R <secondary-user-name> /share/SteamLibrary/steamapps/compatdata/XXXXXXX/pfx
Be sure to replace “<secondary-user-name>” and “XXXXXXX” as appropriate when you issue this command.
Note that this will make the original user unable to play the game, now that we’ve changed the ownership. When the original user wants to play, change the ownership again following the same steps.
This is not ideal, but it gets the work done until this issue is eventually fixed.