By safe, I mean what they run on. Assuming you do your own home network, are their line of products such as cameras, smart bulbs, sensors, and so on secure and private?
I am inquiring for a friend who is looking to put smart devices around his home. He had a bad experience with a house he was renting with those Ring cameras so now he is paranoid about privacy.
Anything that has an option to be used with open source software is safe. I am sure they collect data and information if you use something like Amazon or Google paired with it, or even their own network but if you manually do it, it is fine.
If you are (or your friend is) running a self-hosted network that requires access to the routers, not just the internet, then there is very little to worry about. These products are designed to be opensource for people that know how to use it but also offer the convenience of easy set up through their networks. The reason cameras like Ring are a problem is because they are sent to a cloud and can easily be hacked into or located.
Yes they are, they can be run on your own home network and not even be online at all. This is what makes and keeps them safe. Only people on the actual network in the house can have access to what is being recorded.