“If you are trying to run a native game using Proton but get a Steam compatibility tool error immediately after starting the game, you might have to reinstall the runtime.
Navigate to your Steam library.
In the dropdown above your game list check the Tools option to make them visible.
Search for Proton, right click on each installed tool, visit Properties, open the Local files tab and click Verify integrity of tool files for each entry.
Search for Steam Linux Runtime and repeat the same procedure. If none are available, install the latest Steam Linux Runtime - Soldier.”
According to the archlinux wiki:
“If you are trying to run a native game using Proton but get a Steam compatibility tool error immediately after starting the game, you might have to reinstall the runtime.
Link: https://wiki.archlinux.org/title/Steam/Troubleshooting