If you're wanting something similar to SteamOS right now that has much wider hardware support for your gaming handhelds like the Lenovo Legion Go, ASUS ROG Ally, GPD, Ayaneo or even your laptop / desktop then Bazzite is likely one of the best choices.
It uses the steam deck/big picture ui with gamescope I think. Gamescope(valve) added beta Nvidia support.
So the distros that offer the Steam Deck ui for home theater PC’s are now Strating to support Nvidia. (Think bazzite in game mode, chimeraos and holoiso.)