If you want to use Kiwix as posted by @[email protected] above, you can find the data here: https://dumps.wikimedia.org/other/kiwix/zim/wikipedia/

The latest (January 2024) total dump for Wikipedia (English) is: wikipedia_en_all_maxi_2024-01.zim

…but there’s other languages and sizes available as well.

Important addition: You’ll have to set browser.urlbar.update2.engineAliasRefresh to true in about:config to see the option to add search engines via URL. Otherwise you’ll just see the option to remove them and a link to the add-ons page.