Go to https://kbin.social/magazines and turn on local and federated, then hit the search button. For some reason all the top "hot" are kbin but the "new" and "active" are various.

Then if you specifically want, say, lemmy.world, type that into the search field and hit search again. It will all show.

The article specifically says you can't search federated communities from kbin, but you can from Lemmy. This is just incorrect, both allow you to search local or local and federated.

Click on the tab Magazines at the top, select local and federate, put lemmy.world in the search box to see all lemmy.world communities. If you want to check for community with certain keywords you can try putting [keyword]@lemmy.world. It can search for the keyword in both the name and description, but not extensive as if you'd search on lemmy.world.

This can use some improvement, but it's not a Kbin problem though, since Lemmy is even worse when it comes to searching for communities outside each instance.