installing lulu (application-level firewall) let's you see most (all?) of it. i just wish there was a definitive list of what the endpoint services are. for instance, i have no interest in icloud photo storage, so i'd love to block all those connections at the IP level (not just dns), but i really like using imessage on my mbp, so want to let those through. i'm currently having to figure this out via trial and error (and lots of error, at that).
https://objective-see.com/products/lulu.html