This server isn’t the only one I’m running in the Fediverse :-) I’m currently running these:
https://lemmy.world: You’re looking at it.
https://mastodon.world: My largest server, over 160.000 users.
https://musicworld.social: Another Mastodon server about 1 of my hobbies
https://pool.social: Another Mastodon server about another hobby of mine
https://fotofed.nl: A Pixelfed instance
https://calckey.world: A Calckey server. A bit different from Mastodon.
https://fediland.nl: A Misskey server. Calckey is forked from Misskey, personally I like calckey better.
https://play-my.video: A Peertube server
https://akkoma.nl: An Akkoma server (kind of lightweight but fully featured Mastodon)
https://ruud.social: Akkoma server just for me
https://blog.mastodon.world: My writefreely server, yes that federates too.
More to come probably…
Probably a better list: https://github.com/maltfield/awesome-lemmy-instances