Trending Communities [feddit.nl] gives a list of communities that have had increasing activity for the past week.

It's helpful for a quick overview of possible communities with active discussion, stats too.

https://www.search-lemmy.com/

This one let's you choose the instance you are in so it makes the links open direct in that instance

If you have the patience letting the drip of communities surface through your instances 'all' feed has been a good way to take in the growth.

I have an account I don't normally comment from I leave all the memes unblocked for killing time, otherwise it's been a lot of negative filtering and following interesting comments.

If you're self hosting that's a different problem.

On Lemmyverse, there is the option to set your home instance (top right home icon), then the links open on your instance

https://github.com/maltfield/awesome-lemmy-instances great list of instances to help you pick

Sub rehab is very useful for finding subreddit alternative communities on the fediverse https://sub.rehab/

Search on https://lemmyverse.net/communities

I noticed they also removed lemmy.world from lemmyverse.net so it isn't a very useful site anymore.

Edit: At the moment.

If you use the voyager app they have an option to migrate subreddits using your multireddit. It basically parses the multireddit and allows you to quickly search for communities that match your old subs. It gives you directions to do it. I found it very helpful.

Look at which communities are popular or search for your interests.

I would recommend just going to All communities and clicking subscribe on everything you like.

I haven’t found one, but if you like !Classic Rock come and join us!!