Afaik, whenever an Activitypub instance has defederated from another it has always had to do with some combination of bad user behavior, poor moderation, and/or spam. Are the various instance admins who have decided to preemptively block threads.net simply convinced that these traits will be inevitable with it? Is it more of a symbolic move, because we all hate Meta? Or is the idea to just maintain a barrier (albeit a porous one) between us and the part of the Internet inhabited by our chuddy relatives?
(For my part, I’m working on setting up my own Lemmy and/or Pixelfed instance(s) and I do not currently intend to defederate.)
I’m pretty sure the parent company knows how to deal with GDPR between facebook, whatsapp, and instagram. Whatever issues they faced in EU (most probably the EU’s Digital Markets Act) isn’t directly related to GDPR, because if it was for GDPR compliance alone I guarantee they’d be in the appstore by this evening.