I had a r/w error on /Home, and btrfs couldn’t repair it, so I reinstalled and formatted /Home. Had to add drives in Steam, but some games are not showing as installed, notably Baldurs Gate 3. I was able to verify the files, so I looked at Compatibility and selected Proton (not selected), and it said “Update Required.” I clicked Update and there’s only an hour to go (118 GB), so this might work for you.
What I hadn’t done was going to Settings/Compatibility and selected “Enable SteamPlay for all unsupported titles.”
Oops.