@[email protected] In a sense of groups, as mentioned in other comments, there are 5 to my knowledge:

• Lemmy, created pretty much as a Reddit alternative
• Mbin, meant as a hybrid of Reddit and Twitter’s post styles
• Friendica, similar to Mbin but with a design philosophy inspired on Facebook
• Piefed, which launched with a similar purpose as Lemmy, and dunno how it is now, but in the original roadmap it was meant to have microblogging support too
• Bonfire, which I heard about and that apparently has community-adjacent features, but yet to test.