Seems I was off the mark, as TrueNAS does things differently than pure Docker. According to this thread you need a bridge network and/or to convert Home Assistant to a TrueNAS custom app to get the host mode checkbox.

From my searching, there should be a checkbox called “Host Network” that you can tick in order to put the container into host networking mode.

Since you are running Docker, it’s most likely Home Assistant’s auto discover being blocked by a firewall or port settings or something else along those lines. Make sure the container’s network mode is set to host, and then you have one of two options. You can either manually add the bulbs (not familiar with LIFX but I think it is done by IP address in the “add integrations” part of the devices menu) or find what is blocking the auto discovery so it will find the bulbs and other devices automatically.