I replaced my Nest with a Sensi once Google took over. In doing so, I extensively researched the available options searching for an acceptable one that could be used without a cloud server somewhere, but those just don’t exist in any decent-looking package. Choosing the Sensi was a compromise on settling for a company not likely to go out of business or discontinue the device within the near future and whose core business doesn’t conflict with keeping any data private.

From the Sensi website: "As existing features are enhanced and new features are released, your thermostat software is kept up-to-date automatically."

No thanks. Been there, done that. With a simple device like a thermostat, I don't want the thing changing all the time. Security updates are fine but every update needs to be under my control and the device should be designed with a mechanical switch that restores the previous version of the firmware.

And really even security updates should be unnecessary if the code is written in a type-safe language with good security practices.

I don’t want my complex devices changing all the time either. Just updated my desktop to last year's macOS and it caused a cascade of changes from dependencies I wasn’t ready for. Same with the latest version of Xcode, and the auto-updated text editor that went to subscription for the features I had paid for already.

I got Sensis too. Best compromise I could find, avoided connecting to the internet until I couldn’t find another way to program them. Suppose I could disconnect them now.