Yes. I use it with my whole family. You can create a tracking session and have everyone join in. From the app and the website you can see everyone on the map.

The only trouble Iǘe had is that the Android app sometimes crashes and I have to manually launch it again. There are other compatible apps that I haven tried, though.

If you connect OwnTracks to an mqtt broker, there is a feature to track friends. But I haven't played with that part so ymmv.

I'd hope not. We should normalize less surveillance, not more.

How is it surveillance when two consenting adults share their location with each other using a self hosted service?

Yeah, knowing my SO's location is super important for multiple reasons imo... Primarily safety and knowing how long it will take to get back from someplace (or how long I can keep messing around with stuff at home). I'm sure there's other valid reasons but kinda just provides me peace of mind.

Consent is not a simple binary thing.

Creating expectations around accepting surveillance is not healthy.