My setup is a bit different but I had a lot of fun putting it together. I have a D1 mini with a switch hat wired into the boiler.
The D1 runs a tiny web server that lets me turn the heating on and off. Then I have a bunch of ZigBee thermostats around the house that provide a fuzzy average temperature.
Then I have a custom dash in hass that displays pretty much what a hive would display.
Whole setup cost about $20 and has been running nonstop for over 5 years!