[EquitableEngineer]

You have too much free time on your hands lol Why not turn those PCs into servers on your network. You could have a media server, backup server etc.

what would i do with the servers realistically and what could i run

I was thinking more along the lines of services you can use locally, like Nyx mentioned you could run a plex media server so you can stream all of your movies, music, files etc with any device connected to your LAN. Having a PiHole is also pretty useful or you could run a TOR relay node or host one of the many blockchains out there. If your machines are powerful enough you could install virtualization software on there an run multiple servers at the same time on each machine.

Why not? If you've already got the hardware and it will just cost time, why not learn something new.

I suppose you arecorrect but by for me servers would be a better use of the hardware and by the sounds of things OP would still be learning something.