Yeah, I don’t think “Feed” here is the right name for this actor type. It sounds like it’s just a specialisation of the Group type, perhaps MetaGroup or something — then again, per this thread Proposed FEP-a974: All Actor types should be followable - #16 by trwnh you generally shouldn’t really care that much about the type of an Actor, but rather how it behaves.
E.g., your MetaGroup actor might have a “groups” collection instead of a “followers” collection. I’m not sure what you gain in “following” a group of groups, if it doesn’t automatically aggregate all the sub groups.
It sounds like this would require you to follow each individual group, not just the group of groups.
I think we’d be better leaving a Feed actor type for something like custom subscribable feeds or something, since Feed is just what you’re calling this in the UI of Piefed, not what it actually is: a group of groups.