For example, can I find ActivityPub instances that kbin.social is federating with? I know that kbin.social is federating with fedia.io, lemmy.world, and mastodon.social. Then I want to find other interesting instances. I am also interested in ActivityPub instances that a certain instance is blocking because they may be rather good for me.

There are web sites that are publishing ActivityPub instances, for example:
https://the-federation.info/platform/184

And maybe there are other sites that are publishing federation relationships of instances. However I want to know how to find federated/blocked instances from a certain instance instead of the sites if I can. Doesn’t ActivityPub have such a method itself?

Update: Lemmy instances have their linked/blocked instances list.
https://lemmy.world/instances
https://lemmy.ml/instances
https://feddit.cl/instances

I want /kbin to have the same list!