I'll mention clubhouse.io every chance I get.

It's billed as a Project Management software (and it's great at that) but it can be great for documentation because it:

- provides hierarchical nesting (Milestones / Epics / Stories)

- each object can have a relationship to another (related, blocks, duplicates)

- each object offers a markdown text area, lists, github PR links/integration, comments, and can be moved between various stages (standard scrum stages or your own custom ones)

- each object can be assigned multiple owners, requesters, and followers

- each object can be tagged

- search by title, tag, owner, state, etc.

- each object can have files uploaded and attached

This allows me to track why the work was done, how the work was done, and what work was done, while providing a nice README as a comment.

Everything can be edited, or others in the team can leave their own comments.

It's odd for sure, but I love it.