Old Dell workstation. You probably won’t be able to play anything from the last 10 years, but other than that you can probably play it. Those old workstations are like $150 USD usually, sometimes $200.
EDIT: Didnt see you mention you already have a Steam Deck. For something comparable, you will probably end up paying the same or only slightly less, not worth it IMO. Just stay on Steam Deck for now.