SUMMARY
I tried to compile Plasma on my desktop, but I have a dependency problem when I want to download non-KDE dependencies as explain on this page : https://community.kde.org/Guidelines_and_HOWTOs/Build_from_source/Install_the_dependencies

STEPS TO REPRODUCE
1. Open a Konsole
2. Try "sudo apt-get install libkf5networkmanagerqt-dev"

OBSERVED RESULT
Lecture des listes de paquets... Fait
Construction de l'arbre des dépendances       
Lecture des informations d'état... Fait
Starting pkgProblemResolver with broken count: 1
Starting 2 pkgProblemResolver with broken count: 1
Investigating (0) libkf5networkmanagerqt-dev:amd64 < none -> 5.59.0-0xneon+18.04+bionic+build19 @un puN Ib >
Broken libkf5networkmanagerqt-dev:amd64 Dépend on libnm-dev:amd64 < none | 1.10.6-2ubuntu1.1 @un uH > (>= 1.4.0~)
  Considering libnm-dev:amd64 0 as a solution to libkf5networkmanagerqt-dev:amd64 9999
    Reinst Failed early because of libnm0:amd64
  Considering libnm-dev:amd64 0 as a solution to libkf5networkmanagerqt-dev:amd64 9999
Done


EXPECTED RESULT
The package "libkf5networkmanagerqt-dev" is installed

SOFTWARE/OS VERSIONS
Operating System: KDE neon 5.16
KDE Plasma Version: 5.16.2
KDE Frameworks Version: 5.59.0
Qt Version: 5.12.3
Kernel Version: 5.1.14-050114-generic
OS Type: 64-bit

ADDITIONAL INFORMATION