Bingo! That’s identical to the Haverland API. Good news that two seemingly large European manufacturers of electric radiators have adopted identical tech for smart electric radiators. I ended up running a python script on a RP outside of HA that interfaces the API with HA MQTT climate component and MQTT switches and sensors. It is a crude approach, but it does work. I know that it is possible to create a component based on an API something like this. But I lack the time (and talent) to pursue it at the moment. I will try and post my humble python script to github in the next day or two. I have been super happy with my heaters and now that it seems like the Smart Box tech is being more widely adopted it might be practical for someone to create a component for “official” integration with HA.