A bit more code reading: a conversion to ePub works differently as for example to MOBI (hah, surprise!).
So there is not really one place to remove the extra titlepage (as I understand it mobi displays the cover always before, without extra markup, and this titlepage.xhtml is only generated in the ePub generation).
So removing the Image (Frame, Paragraph) from the ODT seems to be the most compatible way of handling this.
I added code for the image removal. It's a very easy solution, I just need to remove the parent text
element from the document. After this everything looks like I expect it both with MOBI and ePub.
But it's not committed yet, I have to do some more tests to make this more robust.
One question: is it ok to use the mi object to pass the frame id from get_metadata back to the odt import? I would set it as mi._odf_cover_frame