Steam is available on most distro repo's and even if it isn't install it via flatpak and off you go

once you've done that goto settings and steam play and there's a option there something about "use proton for all unverified games" or something, I'm not at my pc to get the direct wording and then you'll be able to install any game from your library and play it

you can use protondb.com to check if games you want to play work on Linux with proton