$ sudo apt -o debug::pkgproblemresolver=1 install kubuntu-desktop
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Starting pkgProblemResolver with broken count: 2
Starting 2 pkgProblemResolver with broken count: 2
Investigating (0) kinfocenter [ amd64 ] < 4:5.2.95-0ubuntu1~ubuntu15.04~ppa1 > ( kde )
Broken kinfocenter:amd64 Breaks on about-distro [ amd64 ] < none -> 2.0.1-0ubuntu1 > ( universe/kde ) (< 4:5.3.0)
  Considering about-distro:amd64 -2 as a solution to kinfocenter:amd64 3
  Added about-distro:amd64 to the remove list
  Conflicts//Breaks against version 1.0.1-0ubuntu1 for about-distro but that is not InstVer, ignoring
  Fixing kinfocenter:amd64 via keep of about-distro:amd64
Investigating (0) ksysguard [ amd64 ] < none -> 4:5.2.95-0ubuntu1~ubuntu15.04~ppa1 > ( kde )
Broken ksysguard:amd64 Depends on libksgrd5 [ amd64 ] < none -> 4:5.2.2-0ubuntu1 > ( universe/libs )
  Considering libksgrd5:amd64 1 as a solution to ksysguard:amd64 2
  Holding Back ksysguard:amd64 rather than change libksgrd5:amd64
Investigating (1) kubuntu-desktop [ amd64 ] < none -> 1.323 > ( universe/metapackages )
Broken kubuntu-desktop:amd64 Depends on ksysguard [ amd64 ] < none -> 4:5.2.95-0ubuntu1~ubuntu15.04~ppa1 > ( kde )
  Considering ksysguard:amd64 2 as a solution to kubuntu-desktop:amd64 9999
    Reinst Failed early because of libkf5sysguard5-data:amd64
    Reinst Failed because of libksgrd5:amd64
  Considering ksysguard:amd64 2 as a solution to kubuntu-desktop:amd64 9999
  Considering ksysguard:amd64 2 as a solution to kubuntu-desktop:amd64 9999
  Considering ksysguard:amd64 2 as a solution to kubuntu-desktop:amd64 9999
  Considering ksysguard:amd64 2 as a solution to kubuntu-desktop:amd64 9999
Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 kubuntu-desktop : Depends: ksysguard but it is not going to be installed
                   Recommends: about-distro but it is not going to be installed
E: Unable to correct problems, you have held broken packages.