There’s very extensive documentation on running your own server: https://solidproject.org//self-hosting/css
And this will answer some of your questions: https://solidproject.org/about
Solid is a specification made for other apps to run on. Here’s a list of apps that have been built on top of solid: https://solidproject.org/apps
This is what a lot of people do when they create a Single user instance. You can learn more about that here: https://calebhearth.com/running-mastodon
There’s other projects that are trying to implement your ‘Earthling’ idea. There’s the Solid project for instance: https://solidproject.org/
I’m really happy with the interface to be honest, I was using Voyager up until now but Boost is my new go to!