mastodon.social, the “default” instance federates. If you have an account there you can see zuckerberg’s profile with this link: mastodon.social/@zuck@threads.net/ without an account this redirects to threads
On other federating instances just search for @zuck@threads.net
helenslunch@feddit.nl 2 months ago
As far as I know, there’s only a manually-configured list of instances that DON’T federate…