I run a few groups, like @[email protected], mostly on Friendica. It’s okay, but Friendica resembles Facebook Groups more than Reddit. I also like the moderation options that Lemmy has.
Currently, I’m testing jerboa, which is an Android client for Lemmy. It’s in alpha, has a few hiccups, but it’s coming along nicely.
Personally, I hope the #RedditMigration spurs adoption of more Fediverse server software. And I hope Mastodon users continue to interact with Lemmy and Kbin.
All that said, as a mod of a Reddit community (r/Sizz) I somewhat regret giving Reddit all that content. They have nerve charging so much for API access!
Hopefully, we can build a better version of social media that focuses on protocols, not platforms.
In response to your postscript: You can search here for other communities: https://browse.feddit.de and there may be other search, please let me know if you find them. That one is a bit slow to update. I used that to determine that there was no community yet for a topic. So I tried to get a feel for which lemmy might be best for it and created it there. The one I created was Trader Joe’s Unofficial You can see I even added a note in the description about it being my first and trying to add a better/more mod.
TL;DR See if your community interest already exists anywhere, and if not, go create it!