Why is this? Is it for pointing clients to DNS or nnot?
daemon.info avahi-daemon[5439]: Joining mDNS multicast group on interface eth1.IPv4 with address 192.168.1.169
Hmm... eth1 is usually your wan connection.
Are you running a network on top of this router?, and do you even want to expose avahi to wan?
otherwise if you don't want avahi to listen on wan you can edit its configuration under /etc/avahi/avahi-deamon.conf and use allow-interfaces=(i.e lan) under the server section.
You can use something like winscp for this just connect to the gateway ip of lan (192.168.8.1) and choose protocol scp, then on the right select the folder and navigate back so you see the etc folder.
username: root
password: same as ui
Avahi works like a proxy deamon, meaning it can help broadcasting multicast groups under multiple subnets via 0.0.0.0, although it is strange it listens on wan, im not sure if that works... that way you may sent multicast groups reversed when there cannot exist two the same both ingress and egress, i think that can conflict, often multicast goes only inbound to the router.
Mdns is often used to discover devices and advertise them one example are chromecasts, avahi makes it extra easier by making it also accessible by other networks.
The reason you may see this is because of network sharing being enabled is my suspicion, but for wan is a little bit too extreme for my liking 