This is why companies want US citizens to believe that EU is a bureaucratic hellscape (I mean there's also the forces that want to tell them it's communist for the same reason I guess)
There is more home shot for them to create new teams. Once they get through everything is when you have to worry about your Google water heater program being cancelled.
Heating systems in Europe are unique and have a variety of hardware and software requirements that make it challenging to build for the diverse set of homes
AKA. Europe probably has hardware and software requirements that make it so Google can't
A) Harvest your data; and/or
B) Must be able to function without an internet connection (aka. they can't kill it)
It's not a hard requirement, but it's sure nice to leave the house at a low but non-freezing temp in winter while you're away for a few days, then use a web app to bring the temperature back up right before you come back in.
Being on the home LAN, though, is a requirement for me. That is extremely convenient.
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
Those "valves" are, in fact, thermostats. They use thermal expansion of wax to open/close the valve to get to their set temperature. Settings 1-5 are 12, 16, 20, 24, 28 Celsius.
We have a Tado system, not the current generation but the one before. It was easy to self-install and configure and has never given us any trouble. There are a couple UX quirks, such as not having a confirm dialog after you touch the Shut Down All or Max Out the Heat buttons, but overall it's one of the rare electronic gadgets that has led to no buyer's remorse.
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.
AC is not common in Europe. There's a variety of heating systems: gas boilers, direct electric heating, district heating, etc. Heat pumps are a growing market though.