I don't think anything really properly compares to FF these days. It's pretty remarkable really, since it's the third online web site in the feederism space I'm aware of, and the second oldest one that's still around.
It's also the only one I can think of that has managed to strike a good balance with fostering a friendly, open community largely free of toxicity and has kept that up for more than 20 years.
A lot have come and go, either fizzling into nothing or turning monstrous or toxic. For the sake of brevity I'm not talking about the ones that are defunct.
FatCelebs/Curvage - It started off as a borderline creepy voyeuristic message board, albeit minus the nudity. Some members would even go around and take pictures of random people. Legally, if you go out in public you don't have the right not to be photographed or recorded, but this still rubbed me the wrong way somehow. Lot of creepy comments though. On one occasion, I think I remember one of the subjects even got doxxed, at which point it turned into danger, and from what I recall that information was up for too long.
Eventually, it devolved into a discount/knockoff version of OnlyFans and ManyVids and has been a simpfest ever since. I haven't checked it out since, since before COVID at least. Whatever it is, it's NOT a place where you can really hope to make any actual, genuine connections, friends or romance.
Grommr - A subsidiary of Grokio, LLC, it's focused pretty much entirely on the gay side of feederism. They do have a competent technical team behind it, but I can't speak to the quality of the community as I've never been.
Feabie - Created by the same team as Grommr as another subsidiary of Grokio, LLC, they have the same solid technical team. However, community development leaves a lot to be desired. I never really interacted on there much, but reports say it's full of toxicity and is very cliquish. Yeah, I don't have any time for that. I haven't checked it out in years either, it's probably worse now, if anything. My recommendation is to give it a pass.
AOL and Yahoo Groups are long gone. Maybe if you get lucky on Reddit? Most boards on Reddit are simpfests and shitshows though, so you'd have to dig through a LOT of crap, but you might find the occasional diamond in the rough.
17 hours