I just enabled Matter in Kasa app and added KH100 hub with KE100 thermostat valves to Home Assistant. I used these already in HA, but through unofficial integration plugin.

Problem: thermostat valves report "heating" whenever they are "on" (i.e. not in anti-freeze mode) regardless of the temperature and open/closed radiator. For example, there's 20°C detected in the room and 18° set, so the valve remains closed until the actual temperature drops below the latter value and there's a need for heating again. But even in this state, Home Assistant shows the device as "heating". While this behavior is consistent with green/grey on/off status shown in Kasa app, it is illogical and definitely needs to be changed both in the app and in Matter. In reality, "heating" is actually happening only when the radiator valve is open. There's no difference between "off" in app (with anti-freeze) and "off" when set temperature is lower than measured - in both cases the valve is closed and "off". I don't know why your implementation doesn't follow this reasoning.

I rely on "heating" (demand!) status to automate gas boiler operation, so swapping the existing HVAC entities with the ones from Matter broke the whole thing. It's really important.

Also it would be great if you could add hysteresis setting or fully manual open/close operation e.g. for floor heating. With external thermometer it is usable, but not exactly what I need.