[Uvix]

You don't even have to convert it, just rename the extension to .kepub.epub. https://github.com/kobolabs/epub-spec?tab=readme-ov-file#sid...

[acabal]

This is not entirely correct - Kobo also expects a bunch of special <span>s inserted for things like highlighting and page numbers to work.

It kills me that Kobo is so close to having plain epubs rendered with Webkit but for some reason they just won't take the leap!