for his second post on Threads, the Head of Instagram, Adam Mosseril: "We're committed to building support for ActivityPub, the protocol behind Mastodon, into this app. We weren't able to finish it for launch given a number of complications that come along with a decentralized network, but it's coming." https://www.threads.net/t/CuRtcYTNY3J
every profile on Threads already has the instance tag 'threads.net' after the username and when you click it "Soon, you'll be able to follow and interact with people on other fediverse platforms, like Mastodon. They can also find people on Threads using full usernames, like @mosseri@threads.net."