My main (and IMO the best) social platform for ABDL stuff is right here.
In the many years I've been online looking for ABDL sites this is the one site I feel is actually full of decent people, sure there are occasionally some creeps as with anywhere and there are always lots of newer folk with some who maybe haven't fully developed their "netiquette" but in general everyone here is decent, polite, helpful, funny, friendly, insightful etc.
Reddit and Twitter have a decent amount of ABDL content and there are good people there but also lots of creeps and because they are massive public platforms for just about everything there is a strong possibility of trolls on there where ADISC is a site you kinda have to be in the community and looking around to really know about or discover, so less trolls.
Discord has lots of ABDL groups and some are OK, some are best avoided, some are small with little activity, and some really need to be deleted for things that they allow/encourage.
I do have a Fetlife account and there is a massive ABDL scene there with many groups from all round the world and quite possibly the largest collection of ABDL people who use it, but there is a lot of other stuff to that many people aren't into so much, there are also a lot of users who go there only to try and hit on people and elicit sexual responses and some real creepers. I tend to only use it to check on events I might like to go to.
Fetlife is, hands down, the number one best site on the whole internet to find events, meets, munches and in general any kind of IRL gathering for ABDL stuff. Definitely not every ABDL event or gathering that runs in the world is there but there are a lot and the people who use the site may well be part of an "unadvertised" group that meets regularly that they can invite you to if you show a friendly disposition.
