I have ESP8266 WiFi modules running Tasmota firmware for a few parts of this. Some report temperature (and humidity just for fun), I like DS18B20 sensors better than SHT30s which seem to have a bit more self heating. Then I also have Mitsubishi mini split heat pumps for which there’s a Tasmota control library. MQTT for communication + HomeAssistant for UI + AppDaemon for automation scripts in Python.

Examples of the UI in HA:

Thermostat controls

Target and actual temperature history