I’m hitting this lately with Plasma 6.2.0. Oddly, it fails to start if I do not specify any backends, but it succeeds if I specify all the backends. But the order matters.
Here are my notes in case it helps someone else.
At first I got nothing until I killed the old process.
$ plasma-discover
^C
$ killall plasma-discover
$ killall plasma-discover
plasma-discover: no process found
Then I got some startup logging, but it would hang quickly and no window would appear.
$ plasma-discover
libs QList("/usr/lib/x86_64-linux-gnu/qt6/plugins", "/usr/bin")
org.kde.plasma.libdiscover: OdrsReviewsBackend: Fetch ratings: false
adding empty sources model QStandardItemModel(0x5bf3e89f78c0)
^C
But when I specified the backends to load and included all of them, it worked.
$ plasma-discover --listbackends
Available backends:
* packagekit-backend
* snap-backend
* fwupd-backend
* flatpak-backend
* kns-backend
$ plasma-discover --backends packagekit,fwupd,kns,snap,flatpak
org.kde.plasma.libdiscover: OdrsReviewsBackend: Fetch ratings: false
adding empty sources model QStandardItemModel(0x5a420195d800)
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:344:18: QML ScrollView: Binding loop detected for property "calculatedImplicitWidth"
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:344:18: QML ScrollView: Binding loop detected for property "calculatedImplicitHeight"
qrc:/qt/qml/org/kde/kirigami/dialogs/Dialog.qml:401:33: QML Binding: Binding loop detected for property "value"
qrc:/qt/qml/org/kde/discover/qml/BrowsingPage.qml:17:1: QML BrowsingPage: Created graphical object was not placed in the graphics scene.
However, I noticed if I specify the backends in the order they were listed, it fails the same as before:
$ plasma-discover --backends packagekit,snap,fwupd,flatpak,kns
org.kde.plasma.libdiscover: OdrsReviewsBackend: Fetch ratings: false
adding empty sources model QStandardItemModel(0x62a8c78bd620)
^C