Home Assistant on RPi with two networks, HomeKit only available on one


I am running HomeAssistant from a docker container (–net=host enabled) on a RPi.
The RPi is connected to two networks: WiFi IOT only, Eth0 “normal” network inkl mobile phones, etc.

Everything is working quite well, except that connection to the HomeKit integration is only made available on the WiFi network. If I switch my iPhone to the IOT network for debugging purposes everything works well, in the “normal” network, I cannot reach the HomeKit integration. Tried both, GUI installation as well as yaml configuration with corresponding IP provision.

Now I am running out of ideas how to tell the integration which network to use. :frowning:
Any help appreciated!