I doubt that there’s a single resource that fits all, but check out Kiwix, team behind Kiwix hoards and redistributes highly compressed wikis and other knowledge bases like stack overflow.
For stuff like coding documentation, I usually just go to the developers main site and they provide it in many formats.
For everything else I just wget mirror (properly throttled, I’m not a cunt) the entire thing once a year.
They probably think if they kill all the witnesses nobody would tell on em 😵😵