For my museum I have Linux (and Minix) running on some pretty old stuff. Workstations & servers (Sun/SGI/HP) still run fine with Linux/Unix on them; those laptops are quite painful if you use X.

I was running Slackware mid '90s and I remember beating my head on the table how slow it was compared to the Sun machines I used in uni with running X. But it beat Win3.1/95 already in my humble opinion so I stuck with it until now (although changed to Debian and then Ubuntu recently). Still allows me to, for most dev, to use laptops from 6-7 years old (my goto dev laptop is a Lenovo X220 from 2011 ; I bought a big stack for almost nothing last year and they are excellent).