mastodon.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
The original server operated by the Mastodon gGmbH non-profit

Administered by:

Server stats:

383K
active users

muesli

@admin

Both exist on Mastodon and the directory is opt-in indeed. Running ElasticSearch on your instance can be pretty painful, but that's the nature of search indexes, I guess.