I decided to revisit some of the Fediverse alternatives to Reddit after nine months.
kbin.social is overrun with spam.
Beehaw is very quiet. Doesn't seem to have much activity.
Lemmy.world is very active in the larger communities, but they all carry that "default subreddit" vibe, full of memes and shitposts. Smaller communities don't have much activity.
I'm really happy with Mastodon. Tonnes of activity, and no shortage of meaningful discussions.