Heard of Combat Master? It's a free to play first-person shooter released on Steam in late April and now it has Linux and Steam Deck support.
Designed to be like a much cheesy faster Call of Duty, one that it's optimized for lower-end systems, it doesn't have anywhere near the level of graphics of the current-gen shooters. It's also a game that was primarily made for mobile it seems, that they've ported over to PC and just recently they added Native Linux and Steam Deck support too.
Notes from the latest update:
- Max players increased: 5v5 and 10 players lobbies are here!
- Lightning speed loading time!
- Steamdeck release, Linux + SteamOS.
- New settting "Toggle Sprint" for Keyboard players.
- Set "Huh" jump sounds volume.
- Sniper Rifles now deal more damage over distance.
- Customize color of Armor Icon in UI.
- Far away shooting sounds are now louder.
- Invert Y-axis setting.
- Warehouse map clipping fix.
They also said the "CombatZone" is coming soon, so probably their own low-end take on a BR like Call of Duty Warzone.
It certainly won't win any awards for originality, and it really is pretty much a bargain-bin poor man's Call of Duty attempt by a small team. That said, it's popular on mobile and even on Steam it seems to regularly have multiple thousands playing it at any time so it seems to have already found an audience. Alfa Bravo Inc (the developers) even say they're just "enthusiasts" who have a "special love for firearms" and the gaming industry with "No corporates" involved.
You can find it on Steam.