I found some hints that Koreader was optimized to read Wikipedia Epubs.
https://fransdejonge.com/2020/10/kor...drops/#respond
I guess those are offline epubs created out of wiki pages.
Is there a source to download or create them, I couldn't find any other hint regarding this information.
Edit: Some afterthoughts later a second guess: Is it to support the online wikipedia feature to export
articles as epub? I guess I was too greedy hoping, that there are some wiki exported fully as epub.