Can’t speak for Twitter as I wasn’t really on it, but Mastodon I pretty much use for the same topics as I use Lemmy, except if it’s a longer more discussion-wanting post it goes on one and if it’s a short casual posts it goes on the other. Don’t bother much with the home feed I just stick with my topics of interest.

Often, I’ll post to Lemmy from Mastodon when something is relevant to both, which means I’m chatting to both groups at once in the replies.

Right now there’s a communal crafting event going on over there with its own hashtag, and tons of people I’ve never interacted with before are taking part, so that’s fun and a nice wholesome time.

It’s just a slightly different format for talking about the same stuff, from my pov.