This is the best summary I could come up with:

Joining the fediverse — the decentralized world of social media that includes Mastodon, Pixelfed, and other services that all interoperate through ActivityPub — has been on the Threads team’s to-do list since the very beginning.

Instagram head Adam Mosseri told The Verge in July that he believed decentralizing the platform was key to making it relevant to a new generation of creators.

Skeptics have long held that Threads would never actually federate, even as Zuckerberg, Mosseri, and others at Meta kept promising they would.

For the largest and most centralized social service on the web, suddenly throwing open the gates to other platforms seemed like an unlikely pivot.

This test appears to only cover one small part of a truly federated social network — it doesn’t sound like you’ll be able to post from Mastodon to Threads, for instance, and you can’t move your account between services.

But the test at least reaffirms Meta’s commitment to ActivityPub and to being part of the broader open social web.

The original article contains 344 words, the summary contains 166 words. Saved 52%. I’m a bot and I’m open source!

They started talking about this a long while back and a lot of instances have already preblocked their domain (mainly Mastodon/firefish/etc but some lemmy instances have too), you can check if it’s blocked or not by going to the instance list and scrolling all the way to the bottom