Unfortunately it looks like kup-backup was orphaned due to maintainer not having enough time for it:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1093521 For the reference, it does pull a bunch of Qt 5 and Kf 5 dependencies, but newer upstream version can already use Qt 6 and Kf 6. Regards, Shmerl.
