With this program, you can create an epub from your unarchived Omnivore items.
Find it on Github: https://github.com/agrmohit/omnivore-epub
Great work by @agrmohit and
Zsolt Botykai.
So I have uploaded this two repos to Github:
- https://github.com/zsoltika/omnivore-calibre-recipe
- https://github.com/zsoltika/omnivore2epub-py
I prefer the first one since Calibre does some magic (converting downloaded images to fit the e-reader screen, removing some not necessary page content).