Offline documentation
Published 2013-05-11, last edit 2020-08-14
Offline documentation reference == speedy access and maybe some tooling included.
zeal is a decent offline document browser on Linux, compatible with dash docsets, one of the first offline document browsers that helped popularize offline browser references). There is even an emacs package for browsing dash docsets.
https://devdocs.io/ is a no setup required documentation browser with offline capabilities (PWA-type of thing).