Some progress here:
- Seems not possible to use ebusctl from within HASS. Not clear why.
- Anyway, installed the ebusd and ebusctl on a separate linux box, and from there I can control the ebusd using ebusctl.
- The mosquito broker can be run on HASS as stated here: MQTT Broker - Home Assistant
Now the question is how to find the right commands to put my Weishaupt heating in day/night modus, and then glue all software components together.
All suggestions are welcome.