Linked in a comment within that post, this appears to be an extremely comprehensive list:

https://kbin.social/m/specialized_instances/t/186667/Big-list-of-specialized-instances

Really love Mander

That’s not the only way. Smaller instances will have very different All feeds because All is just an aggregate of your Instance-mates.

Yeah the All feed shows you the communities that you and all your instance-mates follow, but not every community in existence.

I think a good strategy is to start on Lemmy.World until you discover a solid list of communities you want to follow. Then switch to a smaller instance that aligns with your interests and bring all your subscriptions with you.

If you start on a small instance you’ll have to do a lot more work to discover communities, since they mostly won’t appear in your All feed. Plus, you’re doing that small instance a favor by bringing interesting communities to their All feed.

Well yeah. I guess my question should be “why do we learn indigo and violet when we learn about the rainbow”. It’s more cultural