I like running Linux on older Dell Optiplex systems that you can buy off of Ebay. They usually come with 8GB ram, 256 or 512 SSD and usually 4 to 6 cores (maybe 8). All of the ones I bought use Intel CPUs.

They run Debian or Ubuntu great although I usually run them headless and just SSH into them. One experiment I did was with Talos / K8s with about 3 of these and it worked great.