Facebook! I have made real friends there--people who I eventually met & still liked, & have real relationships with. I've had the same good luck here.

Facebook and only with a handful of people.

Only facebook and I am thinking of deleting my account there.

Twitter, mostly. Some personal stuff on FB, mostly to stay in touch with my daughter, who is pretty much exclusively on that platform. No interest in the others and frankly don't really grok them.

For work I use Slack and Microsoft Teams. I have a LinkedIn account but don't really log in very often. I've had the same primary client for over a decade and so am not marketing myself elsewhere. Meanwhile most of the people who want to "connect" with me seem to be random web developers who hope I'll sub out work to them.

Whats Diaspora? (Well other than the obvious)

None