I'd like to interject for a moment. What you're referring to as Mastodon, is in fact, the Fediverse/Mastodon, or as I've recently taken to calling it, the Fediverse plus Mastodon. Mastodon is not a social network unto itself, but rather another free component of a fully functioning federated system made useful by the ActivityPub protocol, web utilities, and vital social network components comprising a full fediverse.