There's this project called kiwix. Their goal is to provide access to knowledge when there's no internet, so they provide access to lots of trusted knowledge sources: There's books, talks, wikipedia and your favorite software's documentation is probably there too
The first place to check is the library where you can search through the archives. If you click the cards you can open the libraries and browse through the website archives. They even have a search feature that isn't half bad.
It took me a while to find out how to read these archives locally, but here's a good comprehensive list. It seems they have plenty of options, from a simple offline app you can run locally to a little frontend you can self-host that uses the same interface as the library I shared above.
I'm gonna be putting one of these in my cluster to toy with it!