Comment 2 for bug 1899700

Distro packages are not supported here. Distro packages are supported by
your distro.

If you cannot reproduce your problem with
https://calibre-ebook.com/download_linux then it's not a bug in calibre
and you need to ask your distro to fix their intersection of

calibre source code version
python version
qt5 version
various other python module dependencies, or versions thereof

Specifically, the error traceback you reported has been reported several
times here, and continues to be not a bug. You didn't specify the
version of calibre or the operating system you used, but I'm betting
it's a 4.99.x unsupported beta version packaged by debian and derivatives.

tl;dr update to calibre 5.0 or greater, your problems will disappear. Or
tell your distro if they really want to package broken betas, they need
to sync updated versions of those broken betas from Debian, and do so
*promptly*.

 status invalid