For anyone else that's interested, the researcher's own blog post (linked to in the article) gives a lot more detail: https://zerotistic.blog/posts/find-my-people-linux

I was curious if this used rustpush (https://github.com/OpenBubbles/rustpush) to do the heavy lifting and it looks like Zerotistic referenced rustpush/PyPush/FindMy.py in addition to their own reverse engineering to create their own implementation.