I state with confidence, that wiring to a millivolt fireplace/stove/space heater with almost any smart thermostat, including the Wyze, is as simple as;
24v transformer to Rc and C
Heater leads to Rh and W1
Rc and Rh must NOT be connected
This solution has worked for me for years and with several different thermostats.
Did not work for me. With separate transformer the thermostat could not accurately sense room temp. The reading wandered all over the place.
When i isolated the thermostat from the condensing furnace with a simple relay - everything worked.
Which type of isolation the thermostat you are using? 24 V AC Relay? or expensive one?
In my circumstances, none.
Cheers
