I've come across quite a few, but many of them aren't FH-based, like Incandescence, or the Serenity River Pack. As Sig said, Discord has taken over. In my opinion, Discord is simply quicker and easier to navigate compared to online forums :<. Though forum roleplay brings me a fond sense of nostalgia, I now prefer roleplaying in discord. Many groups still keep all their rules and information on forums, however!
Interesting topic, I'm looking forward to reading what others have to say!