I’ve been able to run all of my other regular games since switching to Pop!_OS, but one is giving me a problem still, Space Engineers.
Tried all of the Protons (and Proton-GE), tried various launch options, read all of the feedback left on protondb website for the game, looking for any other ideas. :)
Maybe log out of Steam and sign back in again (I remember CSGO had that happen to me and this step fixed it), updating your computer and packages, restart your computer, uninstall and reinstall the game.