I have a few spare routers accumulated from moving houses, upgrading, home mates leaving theirs when they move etc.

So I was wondering what to do with these instead of throwing them out. Does anybody have experience with using a router as for example a media server, pihole , fan controller for the server shelf …

What OS would be compatible or are routers just to limited in their computational power?

For reference, i have: Speedport smart 4 plus, Fritz!Box 3270, Fritz!Box 7530, EasyBox 804