Just download a copy of a recent wikipedia dump. You can open it in the Kiwix desktop application (work fine even on an old laptop), the android app (though I’ve never tried opening a full 100GB dump with a phone, not sure if it would work well), or install the kiwix-tool package and serve the .zim file with kiwix-serve (wiki.kiwix.org/wiki/Kiwix-serve). You’d also probably want a reverse proxy/usual basic web server/security setup around that.