Also, I should note that the instructions here seem like they do what I want, but they’re outdated. They mention doing everything with LAN and WAN, but there’s a WWAN now. I tried replacing WAN with WWAN, but that didn’t work. I also tried replacing WAN with WAN and WWAN, but that didn’t work either.
My primary router Netgear R6400 does not support WDS, so relayd is the path I’m investigating.