The built-in access to Wikipedia on the Kindle is lacklustre at best. Even if it were out of date, might "the" Wikipedia be available as an epub
for download? Or, perhaps that's such an extraordinarily large file as to defeat the purpose. I would consider even side-loading such a file if it were available.
Individually, it's easy enough to download or convert individual articles for reference, of course. Easy being relative, and, at least with my haphazard approach, a bit unwieldy.