I use old Mac Minis. You can find some decent cheap ones on eBay. They run quiet, have a small footprint and have all the ports I need for projects. I run OpenB

I use old Mac Minis. You can find some decent cheap ones on eBay. They run quiet, have a small footprint and have all the ports I need for projects. I run OpenBSD on them but Linux support is robust for those as well.