I use, in order:

• in instance search
• https://browse.feddit.de/
• user profiles
• the list of instances connected to mine
• https://lemmy.fediverse.observer/

There is lemmyverse.net.

https://lemmy.world/communities

or check “newcommunities”

Maybe any of these will help. !newcommunities@lemmy.world !wowthislemmyexists@lemmy.ca, !lemmy411@lemmy.ca

I mostly search on lemmyverse.net though

I list a few external directories here, although they are currently largely aimed at helping people find a Lemmy equivalent to their favourite subs.