As far as I can tell from my venture into Mastodon’s feeds, the demographics of that part of Fediverse isn’t that different from what Lemmy has: the same political takes, FOSS stuff, “big corpos bad”, etc.
I wonder, is there anything that Mastodon excels at that Lemmy just doesn’t provide? For example, I noticed that there are game developers and artists posting their stuff on Mastodon. Not many game developers (or any creatives, really) on Lemmy though.
For me, one advantage of Mastodon is the ability to follow particular hashtags and for them to show up in my feed, even when I don’t follow the person who posted something using that hashtag. I follow a lot of creative types on there - music folk, writers, artists.
As a corollary, being able to mute particular hashtags is also very welcome!
Mastodon does have a very good muting ability. I like that one can choose what feeds are affected by each word filter. It would be really helpful on Lemmy too.