KCC v5.6.3 is now in pre-release:
https://github.com/ciromattia/kcc/releases
Most important updates IMO are:
1) Fix Mac support, previously wouldn't work with CBZ/CBR, cover upload, damaged when attempting to run
2) Will automatically detect 7z on Windows, no need to fiddle with PATH.
3) Improved error display (no more None error)
4) will crop to fill screen if image is within 3% of device aspect ratio