AFAIK this isn't a built-in feature in ActivityPub and Kbin doesn't implement a migration feature similar to Mastodon.

All you can do is copy your subscriptions from an instance to another (there are tools for doing that with Lemmy, I haven't found any for Kbin), which means you can't migrate your posts to another instance, neither automatically make your followers follow your new profile.

I don't believe so. However, it seems to me like the fediverse, in general, is less bad about you getting access to your data. I would bet you could create software that could migrate a lot between instances.

I had to do that, I basically just made a new account and subscribed to all the same mags by using my old account as a checklist.