I collected some resources that can help in this post, like the aforementioned lemmyverse.net. Another useful trick I’ve found is going to instances dedicated to specific interests (like programming.dev) and browsing their communities list.
The first couple links in my post are kbin specific but the rest should be useful to everybody!
So far I’ve been browsing all-hot and all-newest mainly, to find new communities to subscribe to (and some to block). At some point, probably soon considering the growth in the threadiverse, I’ll switch my home page to subscribed. I comment wherever I feel like it, but I’ve only posted on kbin.social so far.