They specifically mention running WRT on the R1 Plus, so there’s at least some path to using it as a router.
I’m using one of their Orange Pi 5 boards as a Plex server running Debian and it’s been a tank.
NanoPi/FriendlyElec has a ton of multi-Ethernet boards. I haven’t had as much luck with their hardware, but they’re still trucking along, so it might work for you.