Urbit is a personal server, and it's a natural fit for a personal knowledge management system. It can even serve as a community knowledge management system—apps like Quorum gesture in this direction.

A wiki-like system (but likely based on Markdown with internal references instead of Wikitext) would be a straightforward extension from existing capabilities in serving and storing pages.

You could even imagine doing this in sync with an external interface like Obsidian.