Sorry this hasn’t been easier. (I am the Flame Boss developer.) I just ordered a Green and hope to find some time to integrate it with our controllers. If you don’t care about the cloud features (cook history) it might be easiest to integrate directly to the controller on your LAN. Flame Boss and Egg Genius both have brokers built-in listening on port 1883. Just assign them a static IP on your LAN and it should be a reliable way to connect. I’ll let you know if it works with HA after I try it.
I also replied to this thread: