jvalleroy.fbx.one is a Fediverse instance that uses the ActivityPub protocol. In other words, users at this host can communicate with people that use software like Mastodon, Pleroma, Friendica, etc. all around the world.
This server runs the snac software and there is no automatic sign-up process.
I think this article makes some good points. And makes it clear why physics is not a good substitute for philosophy.