Also, there’s kbin, lemmy, squabbles.io (speed- and layout-wise my favorite) - each with several „federated“ instances. Which to chose? For many, the appeal of a social media platform is that you have ONE place where you can be sure to see/read and reach all others.

And instances are sometimes „unfederating“ or the federation is incomplete, you‘ll never know. Just look at this (on reddit, sorry) : https://www.reddit.com/r/RedditAlternatives/comments/149sm0n/beehaw_defederating_from_lemmyworld_and/
If the admin of one instance decides to de-federate, you're suddenly cut off.

I'm enjoying my time on kbin.social and I genuinely support the idea of federation, but... This is honestly the only major issue I have with the Fediverse. Most of my Reddit/social media posts are related to three or so niche interests. My first Mastodon account was on the central hub for one interest that later defederated with the central hub for another interest. Not being able to interact with 1/3rd of the people I want to interact with just defeats the whole point of joining these kinds of platforms. Moderators just carving out a chunk of the Fediverse for their users is just unacceptable.