Since this was the first result in a Google search when I was looking for a solution, I will post my solution here. I created an MDNS reflector with a Docker container to reflect between my secure LAN , IOT -VLAN2, and Guest -VLAN3 networks. Change the specifics to fit your situation.
1- Create docker networks for the VLANs (one time setup in Unraid terminal):
docker network create --driver macvlan --subnet 192.168.2.0/24 --gateway 192.168.2.1 --opt parent=eth0.2 vlan2
docker network create --driver macvlan --subnet 192.168.3.0/24 --gateway 192.168.3.1 --opt parent=eth0.3 vlan3
2- Create docker container:
Name:Avahi (name is used in Post Arguments later)
Repository:flungo/avahi
Network Type:Custom:br0
Fixed IP address:192.168.1.20
Docker Variables:
REFLECTOR_ENABLE_REFLECTOR
Key:REFLECTOR_ENABLE_REFLECTOR
Value:yes
Docker Post Arguments: (ADVANCED VIEW)
; docker network connect vlan2 Avahi --ip 192.168.2.20; docker network connect vlan3 Avahi --ip 192.168.3.20