If you go to the about page of a Mastodon instance, without being logged into, I believe that page will show you any instances blocked there.
Edit: Scratch that, it seems Friendica servers do that, not Mastodon.
If you go to the about page of a Mastodon instance, without being logged into, I believe that page will show you any instances blocked there.
Edit: Scratch that, it seems Friendica servers do that, not Mastodon.