Is there a way to convert a PDF file to ePUB format WITHOUT using Calibre

We know you don't like Calibre... but have you tried its CLI conversion tool?

The Calibre install provides the command ebook-convert that will handle what you want, and there's no need to run Calibre.

ebook-convert file.pdf file.epub

is all that's required.

If the output looks a little wrong - try this

ebook-convert file.pdf file.epub --enable-heuristics

It will try a "smart" way to convert. Not perfect, but can work well in most conversions.

LibreOffice has an epub exporter extension, so you can install the LibreOffice PDF importer extension, import your PDF, and then export to epub.