Not sure if others already said this (I seem to see mostly comments explaining how to do it, but didn’t read them all), but, while it’s certainly feasible, you may not want to do that.

A router is the cornerstone of your network (if it goes down, so does the network) and if you are a self-hoster you’ll probably fiddle endlessly with your home server, and of course break it from time to time… the two things just don’t go well together.

Personally, I’d recommend getting some second-hand router appliance that can run openwrt and use that (make sure to check the flashing procedure before deciding what to buy - some are easier than others). Or you could get a dedicated x86 machine… probably overkill though.