Writer cannot export directly in ePub 3.3.
Is this a must?
There is a lot of improvements (from security breaches to better e-reader management).
Is this a hard thing to implement?
Thanks
No, but it needs somebody who will implement it.
You may file a request of enhancement at bugzilla.
My first impulse for security is to stay on epub2, as the new version allows also JavaScript…
Your other point leads to the question how to do this in Writer. So exporting to epub2 would maybe not solve your problem.
Depends on your experience…
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But actually: Yes it is. From description it is not just some little extension to epub2 but seems to implement a lot of html5, css and multimedia-support, so you have to convert not only text but also a bunch of implemented graphics and video.
On top of that you should convert all the new accessibility-information. This is a nice thing to have, but definitly nothing you just implement in an hour (Maybe our new vibe-coders can …).
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It may be quite easy to extend the current system to write epub3 instead, but that would not implement/use any new feature. It would be ebub2 with a new label.