I encountered the same error message, yet it seemed to be from a broken link instead. From the homepage [0] while signed in, I clicked on "How to play" right under the query entry box. It sent me to this page, which is a different url from the one you linked: https://wiki.github.com/Abstrct/Schemaverse/how-to-play
That should link directly to the tutorial (link above) instead of that wiki anyways