If you go to "Moderated Servers" in your instance "About" page, you can see a list of blocked and limited servers. In Mastodon servers that have blocked Threads you can see a list of what the moderators blocked.
Here's an example from mastodon.ie. THREE PAGES of servers for Meta and this isn't even half of them.
(For the visually impared, there's nothing very interesting on these screenshots. it's literally just long lists of suspended Meta servers.)