You should slso add that you share on #nostr too.
As of today Mastodon protocol is used to share notes between Mastodon and other AP apps like Peertube, Pixelfed or Mobilizon. Try to post, mention a Peertube account from Pixelfed, or subscribe to a Mobilizon event from Peertube, AP is there but communication is not (yet ?) possible. AP is already 7 years old. May be one day each app will be able to talk directly to each other.