Hitch and JSWolf thank you for your advice, even if it does not solve my problem.
Probably like many non-European members of this forum, you are not aware of the so-called European Accessibility Act.
We started making a template in ePub3 format not just as an experiment, but because within about two years all European publishers and retailers will be obliged to sell only and exclusively ebooks that are fully accessible. And this means creating new ebooks and updating already published ones that perfectly follow the accessibility standards of ePub3 and WCAG 2.0.
Thus, from June 2025 maintaining compatibility with ePub2 reading devices will be totally out of the question, not because it is not technically possible, but because the law will impose the sale exclusively of ebooks in ePub3 format.
The European Accessibility Act – how does it impact publishers?
So I hope you can put yourself in the shoes of a small publisher like yours truly, who is already starting to go crazy to make his catalogue compatible with the incoming European Accessibility Act.
Thanks anyway