SteamOS has been out on Steam Deck for 18 months, but still no general release in sight. I wouldn’t hold my breath. I think we’ll just have to continue to make do with the likes of ChimeraOS/Nobara.
I honestly think it’s just because most people have nvidia and steam on linux and nvidia don’t work well together and linux and nvidia and just nvidia in general. It works enough but is not a smooth experience. Maybe once the open source drivers are fleshed out more it’ll be better