Primarily Lemmy and Mastodon to replace Reddit and Facebook respectively. Those are the only social media platforms I used extensively, really, anyway. And I’m hosting a Mobilizon instance to replace the lost event organizing of Facebook that moved to chat rooms on Signal for now.
I never used Twitter really because Facebook filled that need and more. I might eventually go to Friendica, or at least have considered it. Basically, at the time, I was looking for two kinds of communication/conversation. One topic based and one user based. The user based side has two parts, friends and content producers. Since i don’t have many friends on the fediverse, that side isn’t as easy to fulfill. Lemmy covers the topic based, and Mastodon covers the user based for content producers well. If I get more friends converted, I’d probably be more interested in Friendica.