I can also confirm that there are only basic controls available in HomeAssistant for the MTS300. I need to be able to control the Fan and Aux modes, and currently the firmware does not support this. Also, be aware that if you do not have Google Home, HomeKit, or SmartThings, that it does not seem possible to get the App to work. I had to do the initial install with the Meross app, and then switch over to HA for the matter pairing. after which the app didn’t see the thermostat (and HA could only control basic settings). This would probably be easier fi you already have a matter ecosystem.