Verification - Mastodon
[https://joinmastodon.org/verification] - - public:mzimmerm
Shows instances with a series of questions, can sort by size. Mastodon.social has almost a million users
Describes some apps that show followers on Twitter that are also on Mastodon. You can use tools like Debirdify and Fedifinder to look for people who have shared their Mastodon handle on Twitter.
List of mastodon servers