Calibre will work for this, but it almost certainly won't give a good result. That's not Calibre's fault; Adobe InDesign produces exactly the same horrible output from a PDF. It's just a reality that PDF does not lend itself gracefully to being converted easily to a well behaved EPUB.
Unless you are converting something extremely simple with no inline images or interesting text layout, getting a nice EPUB will almost definitely be a tedious process of fiddling directly with the HTML and CSS with something like Sigil (or Calibre, but it's not as nice).
Your comments are not wrong, but also Trump is not the sole issue here. There would still be a problem even if he was removed from office today.
Proprietary software and services are an issue regardless of which government jurisdiction they fall under. It's a good idea for the EU to be moving to open source instead of proprietary solutions based in the EU.