I use a cluster of P51s for homelab stuff which includes running Bitcoin stuff.

An old laptop with a new SSD would be what I’d recommend buying overall, as it can work and be the least to purchase. There are old business PCs that are pretty cheap used as well. The rasp will be rather slow to build the chain overall. I think for some folks takes 2 weeks :/

Next upgrade for me would be Framework with the Cooler Master case in order to standardize on a form factor, hoping for an eventual rack mount case.