I can’t think of many companies I would be less willing to buy home automation tech from than Google.

I built a thermostat with a Wemos D1 mini and a relay module about 10 years ago.

Still use it today integrated with home assistant and can turn the heat on and off while away from home. It’s been reused across three boilers, no parts replaced.

It was a really fun project and I had virtually no experience with Arduino when starting out. Would recommend it to anyone.

TBF, over 15* in Germany I’ve only seen a couple of actual thermostats. The vast, vast majority use a valve on each radiator. There are electronic solutions for the radiators, but sticking a Nest on the wall is going to do nothing for someone unless the customer installs specific hardware that the Nest would have to support

*edit : years

Anyone in Europe looking for an alternative might want to check out Tado