Hexbear was largely not federated with anyone, they were their own site called Chapo.chat for a while, then Hexbear, then they started federating. Lemmy.world defederated from Hexbear before Hexbear even federated with Lemmy.world, but most instances retain federation with Hexbear. Hexbear did defederate from blahaj.zone and sh.itjust.works though, among others.