Import epub: Xml masking gone wrong

I just uploaded the Thomas Mann’s Mort a Venise
(in French, from the publoc domain site https://www.ebooksgratuits.org/ebooks.php; tje book is on the public shelf) .
The ebooks has a lot of formating like italics, dashes, etc.
On my normal ebook reader these XML elements get translated properly.
Readlang however is showing me weird Markup like
& rsquo; & ndash; …

Would it maybe be possible to implememt better encoding for XML formatting?

maybe you can convert it to txt temporarily.
EPUB to TXT (Online & Free) — Convertio

What always works for me is converting it from epub to mobi and then converting again back to epub. This has always fixed it for me. There is dozens of free online convertors.