I am using a system-installed Steam, but sometimes a Steam Flatpak can help with troubleshooting, because it bundles components inside of the flatpak. Running games this way may give you a 5% performance penalty, but it's a good way to see if you have a packaging issue (other things needing installed, or misconfigured).

Also are you running th Linux native one or the proton version?

I run everything through Steam with the proton compatibility layer forced. It's a steam client option somewhere.

I think they're an app called ProtonQT or something like that. It will enable you to easily download the latest proton-ge version. Once downloaded and installed you will need to restart the steam client, then restart the steam client again after selecting the new proton-ge version as the default.

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https://www.protondb.com/app/255710

The Steamdeck loads games into some kind of nested x11 renderer-in-a-window, I think. If for no other reason than to try to avoid Wayland’s extra input latency? Dunno. Maybe you lost some component it needs to work, if regular Steam also does that.