Some good responses so far.
There are, or used to be Kik groups of various sorts, of varying quality with most being quite toxic, or more dead than Disco. You need to have a very thick skin.
Whisper in general is a big mess, and your posts won't show up half the time because of overzealous spam filters, but there's a few groups on there. But again, Whisper is toxic and you need a very thick skin.
Probably dating myself somewhat, but..
I've looked around on various IRC (Internet Relay Chat) networks. Very little/almost none that refers to feederism, though on occasion I might see a channel that refers to BBW. One such Feederism web site used IRC for their chat, but that didn't last long and they moved to Discord, unfortunately.
Not an option anymore but I remember the old Yahoo groups. Never really used UseNet, but there were probably newsletter groups. But as a protocol, it's so niche now that I wouldn't recommend it.
I'm not just saying this because I'm staff on here, but so far I think FF has done the best job so far with a welcoming, accepting feederism community. That's in spite of various quirks, or that the chat is web based which isn't what I prefer. It's the only online community I've kept coming back to for nearly 16 years, and that's saying something.
2 years