We ran the Leuven community detection algorithm on popular users on Bluesky (where the graph has edges determined by Jaccard similarity of a users' followers).
We identified 118 communities and based on the names and descriptions of the top 10-20 users had LLMs generate title and descriptions for them.
There are communities like "Feline enthusiasts", "Web Professionals", a bunch of NSFW ones and quite many communities are many different flavors of progressive/liberal activists.