I'd suggest you take a look at the @usernames of commenters in communities you like then lookup their home instance list. This list can be found at: instancename.here/instances Example: admin@lemmy.ml is hosted on the Lemmy.ml instance. Therefore: https://lemmy.ml/instances
This will bring up a giant wall of text. First heading "Linked instances" are those federated with, second "Blocked instances" is those not federated with. Using Ctrl+F, "Find in page" or "Find" is incredibly useful here.
Hopefully this'll help you now and in the future!
I feel OPs got a really good site and this is their way of sharing the good word! Reverse psychology at its finest!