Hi all, I have a project in which I have an iframe that contains a html file that simulates a flip book. I want to publish it as an epub. When I was trying to test it with Adobe Digital Editions, I got validation issues regarding the lack of fallbacks for the iframes.
I have searched for solutions on the web with no success. How can I solve the problem?

Fallback must be provided for foreign resources, but found none for resource "OEBPS/assets/folders/1-BOOK_FRONT_MATTER_EN/index.html" of type "text/html".