API access is being ended as well, so third-party apps and services will not work.
I was hoping that at least my Home Assistant integration would keep working. That sucks terribly. Lesson of the day: Avoid any IoT device that you can't use without an external service.
FWIW, I replaced my Nests with Centralite Pearls a few years ago, and have been extremely happy with them WRT Home Assistant. The Pearl doesn't seem to be widely available anymore, but any Zwave or Zigbee thermostat + a local hub gets you a thermostat that should work with Home Assistant and will be immune to being sunsetted like this.