I had a 2950 nearly 10 years ago and they were old then. Hopefully you didn't pay for that jet engine?

Can you be a bit more specific about the error to narrow down the problem?

I don't think it's realistic to find something low energy, easy to setup and cheap. I wouldn't go with a Pi 5 as I don't think it will do everything you are hoping for. I would look at a used SFF desktop and chuck in more memory and a few SSDs. That wouldn't cost a lot and has a lot of potential.