This is one of the reasons I am working on an enclosure-compatible open-source version of the 2nd gen Nest thermostat. It reuses the enclosure, encoder ring, display, and mounts of the Nest but replaces the "thinking" part with an open-source PCB that can interact with Home Assistant.
Nest has been pretty-badly supported in Home Assistant for over a year anyway, missing important connected features.
I've got the faceplate PCB done and working; the rotary encoder and ring working; and the display working but with terrible code with a low refresh rate.
I need to ship at the end of October to beat the retirement date. Plans to get some regular development report-outs and pre-orders are coming quite soon.
It's open source, and uses ESP32-C6 so it can be Wifi, BLE, or Zigbee, whatever software you intend to load onto it.
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