Any random Linux distro or Free/OpenBSD install doesn't need an account of any kind. Unless you need an awkward modem which is hard/costly to get (e.g. cable in

Any random Linux distro or Free/OpenBSD install doesn't need an account of any kind. Unless you need an awkward modem which is hard/costly to get (e.g. cable internet, VDSL2+), almost everything can be a decent router. Commercial routers often have some kind of hardware offloading for routing built into their SoCs, but you don't really need that per se at residential internet speeds (<=1 GBit/s). I'd recommend to separate router and wifi AP because this lets you pick the optimal place for the wifi AP regardless of where the internet cable is. Somewhat more costly but likely worth it for anything bigger than a three-room flat.