Targeting Windows and Proton is already the status quo if you want the green tick on Steam, and apparently tens of thousands of game developers do because Valve

Targeting Windows and Proton is already the status quo if you want the green tick on Steam, and apparently tens of thousands of game developers do because Valve promote Deck-compatible games heavily and that audience is more likely to spend money. You can build a "Steam box" console with any Linux distribution and Steam's Big Picture mode. Autologon and start Steam in Big Picture mode on startup. I have this on Debian on a NUC, and there's a distro ChimeraOS which offers a polished pre-installed A/B update experience too.