There was a job offer on ElixirJobs in April from a company called moodle who were looking for an Elixir dev to help them with their project which was some kind of a social network implementing the ActivityPub protocol.
Apparently that project is open source: MoodleNet / MoodleNet Backend · GitLab
That ActivityPub spec looks rather complicated not sure if this is something you’d want to start with but it might help you or inspire.
