tex4ebook includes the cover as the first page of the book. However, the Kindle automatically includes the cover as the first page, getting the cover from the OPF file. The result is a duplicate cover page. (Section 3.2.3 of the Kindle Publishing Guidelines says "Internal Cover Must Not Appear Twice").
Is there a way to specify the cover image so that it goes into the OPF file, but not into the HTML? Thanks!