I found this website really helpful. It rounds up subreddits that existed on Reddit and the places they’ve moved to in the Fediverse.
Reddit Migration
### About Community Tracking and helping #redditmigration to Kbin and the Fediverse. Say hello to the decentralized and open future. To see latest reeddit blackout info, see here: https://reddark.untone.uk/
I seen this. I'll have to spend some time browsing the entire thing. So many subs.... Can't support by popular or most subscribed. Lmao.
https://lemmyverse.net/communities and https://browse.feddit.de are two great Lemmy community searching tools. Is there anything similar for kbin?
Connect for Lemmy currently doesn't have a great community browser (hopefully that will change soon). What instance are you on? If you are on lemmy.world they have a pretty good community browser here: https://lemmy.world/communities. You can filter it to just search local communities (on lemmy.world) or all. Other instances probably have similar community search options.
I don't know anything about the mobile apps for the fediverse, but you can definitely search for communities from the Lemmy web UI (same goes if you're on kbin). If you go to the Communities tab there should be a search field in the upper-right.