You don’t need SteamOS to play games via Steam on linux. Just use any linux distro (preferably one that supports newer gaming hardware), install Steam, go to Settings > Compatibility and “Enable Steam Play for all other titles”. There’s a drop-down that let’s you choose different Proton Versions (some work better than others, hence the config-reviews on ProtonDB to see what works).

For gaming you can just use steam. You can see which game works and the corresponding distributions/configurations on ProtonDB; Helldivers 2 get’s a GOLD status (https://www.protondb.com/app/553850).

:)

Important addition: You’ll have to set browser.urlbar.update2.engineAliasRefresh to true in about:config to see the option to add search engines via URL. Otherwise you’ll just see the option to remove them and a link to the add-ons page.