Fun fact: you can't illegally download all of Wikipedia, because you can only do it legally. The English Wikipedia is less than 100 GB with images and half that without images. You can also download the top 50,000 article, which with images, are less than 7 GB.
See @[email protected] (I'm not sure how well-supported cross-galaxy mentions are here or if they even work)
edit: see Kiwix.org