Tim Bray, one of the XML pioneers, a colleague of mine at Sun Microsystems when I worked on the Atom specs for blogging, wrote an overview of Mastodon but does not mention #Nostr. See my reply to his post.
nostr:note1ra5sp2ms703xetzjw6y5kd6nauu2gm2wky3ra8dvvkptxt68m90q3uyw4v