I’ve got two services on my computer. One is for email, I want that this port to be open to the public WAN and one is for immich which hosts all my private pictures, I don’t want this port to be public but reachable on LAN. In my router I open the port for email but not for immich. Emal can communicate on LAN and WAN and immich only on LAN. On a foreign, untrusted LAN, like an airport I don’t want other people being able to sniff my immich traffic which is why I have another firewall setting for an untrusted LAN.