For the moment kbin doesn’t offer the possibility of blocking an instance. The only possibility if offers is to “silence” it, that means, the user don’t see the posts from this instance, but the instance (Meta in this case) can access the data posted by the user.
Kbin is a quite young project, and it is still in development, then for sure the implementation of a real block/defederation feature will take a lot of time.
I was wondering whether some of the new kbin instances have decide to defederate from Meta. I was not able to find the information.
In other case I will need to delete all my posts, find new moderators for the two magazines I started, and delete my account without to have another alternative.