This does not seem to be working; whether it can/should work in a routed world is less clear.
I don’t see this as highly important right now, but maybe someday…
I note that guests should NOT be able to access printer resources on the secure lan.
As for addressing this:
samba can run on the router, providing a central rendezvous point for
mdns - if implemented, and I thought it was in cups LONG ago, should also be able to do the trick,
but this would be a good test.
To confirm this theorya, we need to do a little bit of wire sniffing.
This begs the question of how common this use of snmp broadcast is in other applications and operating systems.