Calibre 4.99.4+dfsg+really4.12.0-1build1 fails to open qt5ct?

[chris_debian]

Calibre fails to open from application menu, in Linux Mint 20 Cinnamon 64-bit.

Also fails to open from terminal.

Error in terminal refers to qt5ct:

qt5ct: using qt5ct plugin
Traceback (most recent call last):
  File "/usr/bin/calibre", line 20, in <module>
    sys.exit(calibre())
  File "/usr/lib/calibre/calibre/gui_launch.py", line 73, in calibre
    main(args)
  File "/usr/lib/calibre/calibre/gui2/main.py", line 543, in main
    listener = create_listener()
  File "/usr/lib/calibre/calibre/gui2/main.py", line 514, in create_listener
    return Listener(address=gui_socket_address())
  File "/usr/lib/calibre/calibre/utils/ipc/server.py", line 110, in __init__
    self._listener._unlink.cancel()
AttributeError: 'NoneType' object has no attribute 'cancel'

[Eli Schwartz (eschwartz)]

This is an unofficial hacked-together Debian-specific modification on
top of an unreleased beta build that should never have seen production
use. Debian testing provided it while iterating on the beta, but moved
to the calibre 5.0 release and never provided a beta in a stable version
of Debian.

Ubuntu then included this beta build into their stable LTS, and I
presume Linux Mint got it from there.

Please upgrade to a 5.x release, or downgrade to the final 4.x release
which was 4.23; no support will be provided for this Ubuntu thing.

If your distro does not provide a decent version of calibre that
actually works, you can get a decent version from
https://calibre-ebook.com/download_linux

 duplicate 1898904

[chris_debian (cjhandrew)]

Apologies for creating the duplicate. I checked for the keyword qt5ct, and didn't find any existing bugs. Thank you for taking the time to reply.

Chris

[Eli Schwartz (eschwartz)]

The error message doesn't mention qt5ct. The mention of qt5ct is a
status message that occurred before the error.

You'd get the same error if you tried running calibre without qt5ct.