"Kiwix is by far the largest offline distribution of Wikipedia to date. As an offline reader, Kiwix works with a library of contents that are zim files: you can pick & choose whichever Wikimedia project (Wikipedia in any language, Wiktionary, Wikisource, etc.), as well as TED Talks, PhET Interactive Maths & Physics simulations, Gutenberg Project, etc."
Wikipedia provide free downloads:
https://en.wikipedia.org/wiki/Wikipedia:Database_download
And Kiwix is open source software that supports Wikipedia on most platforms for free:
From: https://en.wikipedia.org/wiki/Wikipedia:Database_download#Ki...
"Kiwix is by far the largest offline distribution of Wikipedia to date. As an offline reader, Kiwix works with a library of contents that are zim files: you can pick & choose whichever Wikimedia project (Wikipedia in any language, Wiktionary, Wikisource, etc.), as well as TED Talks, PhET Interactive Maths & Physics simulations, Gutenberg Project, etc."
https://www.kiwix.org/en/