In my book, I caution about the efficacy of online forums and groups to deal with mental health issues. In the first days if he Internet, I was an early user of newsgroups but abandoned those forums. It was one of the cures I tried that ultimately didn't help. The problem is that the suffering is deep and wide and the help can be far between. I recently checked in on some Facebook groups. There was a tidal wave of despair and a few people offering useful advice and support. So many of the responses were people piling on with their own suffering. After a bit, I had to get out of those groups as they began to feel like psychic quicksand.
I think that curated groups can be helpful. I have seen some very good groups related to (ACT) Acceptance and Commitment Therapy. Having a therapeutic focus means that new people are meeting people who have had some success. That's a good thing. And, the creator of ACT, Steven Hayes, suggested a site called The Mighty. I have found a diverse and compassionate community there. I will keep looking.