Docker container does not find bridge

Okay, so I am running Roon as a docker container on a host with strict firewall rules. While I can connect to the core, and it also finds all my Sonos devices, it does not show me the Roon bridge that is running on the same subnet. This works when I am completely disabling the firewall rules.

Currently I have 1900/udp, 9003/udp and 9100-9200/tcp whitelisted. What am I missing?

inbound and outbound?

Why not allow your subnet, You do not trust your subnet?

Well, I am not sure if outbound or inbound is the issue. So any hint would be useful.

Subnet is an interesting idea though. Perhaps I’ll give that a try.