Google announced the end of support for early Nest Thermostats in a support document earlier this year that largely flew under the radar. As of October 25, first and second generation units released in 2011 and 2012, respectively, will be unpaired and removed from the Google Nest or Google Home app.
Users will no longer be able to control their thermostats remotely via their smartphone, receive notifications, or change settings from a mobile device. End-of-support also disables third-party assistants and other cloud-based features including multi-device Eco mode and Nest Protect connectivity.
I mean, I’m not a trained tech, but it isn’t hard to open up the heat pump and look at wires going in and looking at the thermostat and making sure they match. Although I admit someone ran stranded wire instead of solid core (one day I might try to fish a new wire). For now I just tinned the ends.