I have Ubuntu 18.04 LTS MATE installed.

The system is fully upgraded, does not have PPAs and/or thirdparty repositories added.

I have installed Plasma Discover by the following simple commands:

sudo apt-get install plasma-discover \
plasma-discover-flatpak-backend plasma-discover-snap-backend

When I try to launch it from GUI - it does not open.

If I try to open it from terminal I get:

$ plasma-discover 
QQmlApplicationEngine failed to load component
qrc:/qml/DiscoverWindow.qml:3 module "QtQuick.Controls" is not installed

Errors when loading the GUI
no packages for "org.gnome.DiskUtility"
no packages for "org.mate-desktop.mate-eiciel"
no packages for "org.gnome.DejaDup"
empty appstream db
setting currentApplicationBackend PackageKitBackend(0x557c7d4a1c00)

What should I do to fix these errors?

1 Answer 1


I reported bug 1788863 about missed dependencies.

Afterwards I visited packages.ubuntu.com and found necessary dependency - package qml-module-qtquick-controls.

Installation of it with

sudo apt-get install qml-module-qtquick-controls

But this is not enough, here is other error message:

qrc:/qml/ReviewDialog.qml:3 module "QtQuick.Dialogs" is not installed

so we need to install other package

sudo apt-get install qml-module-qtquick-dialogs

fixes the problem - Plasma Discover starts and works normally:

Plasma Discovery on Ubuntu MATE 18.04 LTS

During its operation it was discovered that it needs kded_kcookiejar from kdelibs5-plugins package.

So the complete command to use Plasma Discover is:

sudo apt-get install plasma-discover \
plasma-discover-flatpak-backend plasma-discover-snap-backend \
qml-module-qtquick-controls qml-module-qtquick-dialogs kdelibs5-plugins

Note: this method is actual for Ubuntu 18.04 LTS with GNOME Shell too.

  • 1
    Someone else had a similar experience. One of the KDE devs had written this: "Yes, Discover should definitely work in other desktop environments. However, what you describe is a packaging issue in Debian; packages that are required aren't getting installed by default, boo! This is probably masked by the fact that the missing packages are always installed for other reasons in a KDE Plasma environment, so nobody noticed that the Discover packaging wasn't marking them as dependencies correctly."
    – DK Bose
    Aug 24, 2018 at 13:31
  • 1
    Thank you for the link. I discovered, that ...dialogs is also needed. Just tested on GNOME, we need to install two dependencies manually.
    – N0rbert
    Aug 24, 2018 at 13:52
  • 1
    By the way, Lubuntu Cosmic has Discover installed by default so I couldn't check for missing dependencies :)
    – DK Bose
    Aug 25, 2018 at 9:02
  • Hey, when are you going to drop by chat sometime? :-)
    – Fabby
    Aug 28, 2018 at 21:09

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