For when I want to keep track of stuff that's connected directly to the projects that I work on, OpenProject has Wiki functionality built in: https://www.openproject.org/docs/user-guide/wiki/

For when I want to keep track of stuff that's connected directly to a particular codebase that I'm working on, turns out that Markdown files within the project's repo are more than sufficient.

Nothing wrong with BookStack, of course, it just felt like I didn't need it as a separate system.