Description of problem:
There is always a toast message saying "Please make sure that Appstream is properly set up on your system" whenever I launch Discover.

Version-Release number of selected component (if applicable):
plasma-discover-5.20.5-3.fc33
plasma-discover-5.21.3-1.fc34

How reproducible:
Always, on both wayland and x11 sessions.

Steps to Reproduce:
1. Install Fedora 33/34 KDE spin
2. Launch Discover
3. Observe the toast message

Actual results:
There is always a toast error message.


Expected results:
There should be no error messages out of the box.

Additional info:

On F34:
$ plasma-discover
file:///usr/lib64/qt5/qml/org/kde/kirigami.2/ActionToolBar.qml:109:18: QML ToolBarLayout: Binding loop detected for property "actions"
invalid kns backend! "/usr/share/knsrcfiles/servicemenu.knsrc" because: "Config group not found! Check your KNS3 installation."
kf.newstuff.core: The CustomName property is deprecated and will be removed in KF6
kf.newstuff.core: The ChecksumPolicy feature is defunct
kf.newstuff.core: The SignaturePolicy feature is defunct
kf.newstuff.core: The ChecksumPolicy feature is defunct
kf.newstuff.core: The SignaturePolicy feature is defunct
adding empty sources model QStandardItemModel(0x55f4f2bdf160)
org.kde.plasma.libdiscover: Couldn't find a category for  "fwupd-backend"
Could not open the AppStream metadata pool "Many components have been recognized as invalid. See debug output for details."
file:///usr/lib64/qt5/qml/org/kde/kirigami.2/private/PrivateActionToolButton.qml:74:5: QML Binding: Binding loop detected for property "value"
warning: xnack 'Off' was requested for a processor that does not support it!
warning: xnack 'Off' was requested for a processor that does not support it!
The Theme singleton is deprecated (since 5.39). Import Kirigami 2.2 or higher and use the attached property instead.