Facebook claims that the data they have on people cannot be understood by the average person, and because the GDPR requirements state that data needs to be given in an easily understood format, giving this data would violate the law. So they refuse to give it.
This was after months of simply ignoring the requests.
Seriously.
Names of your friends and timestamps of when you added them. That's all. This is just so ridiculously useless for anything but compliance.
Besides that, there are no user/group/post/whatever IDs anywhere. Everyone and everything is referred to by names and names only. It's hilarious.