Cheap test server for ~100 bucks?

I would like to add a test server to my homelab, where I can tinker around and test stuff without having to worry about breaking anything. It's mostly just for educational purposes, where I try new stuff out (like Proxmox or TrueNAS instead of Unraid, which I'm running on my current server).

I was thinking of a budget of around 100 Euro/USD, for which I could get something like an EliteDesk G3/G4 mini. I don't need the system to be fast, reliable or low in energy consumption, but ideally it should be small and somewhat quiet. I tried googling and searching here on Reddit to see if other people have talked about this, but haven't found anything so far. Does anyone have a recommendation for me what I could get?