[mason55]

The whole philosophy behind HA is "local only as much as possible".

There are a few analytics modules that report back which integrations are in use so that they can help focus dev efforts but those are optional. They also have a cloud service that can be used to help expose your instance externally if you don't want to run a local nginx and expose your home network to the outside world, but even that is not a way for them to monitor the devices you're running.

Plenty of people run HA with absolutely no access to the outside internet (like, the host is firewalled from communicating outside the local network). Plus it's all open source so you don't need to trust anyone, you can look at the code if you want.