Finding zim files
Kiwix uses the openZIM format. Websites are compressed and stored as .zim files.
Requesting new content
Zimit is a tool that will allow you to convert almost any website to the zim format. Try it!
If Zimit works but the website is too big and exceeds the allowed threshold of 1’000 pages, open a request on Github (it has to be freely licensed content).
You are the owner of that content or need a specific distribution method (e.g. as an offline app), get in touch!