just a note, steamos is designed to replicate the experience of a console and is not great as a general desktop os, as valve themselves state here. i'd recommend against steamos and would recommend something more like ubuntu or manjaro. since steam machines failed, steamos seems more like a controlled testbed for valve which they use to develop and test linux stuff (kernel patches, drivers, proton) before they send the patches upstream

that said, steamos should be fine if you just want to turn that 2nd rig into a console and by it "becoming a testbed for valve" i dont mean it is unstable or anything like that.