I'm using Fedora 34 w/ the KDE/Plasma spin (Plasma v5.22.4, KDE framework v5.85.0)

I generally use the Discover app to install software updates. Occasionally, when I reboot to install the updates offline, the offline update task fails. When this happens and I log back in after the reboot, the Discover app displays a dialog in the bottom right corner of the display that says, for example,

Discover
Offline Updates
Failed to update 1 package
cannot update repo 'fedora': Cannot prepare internal mirrorlist: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metal ... rch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]; Last error: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metal ... rch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]

The "Offline Updates" dialog has a "Repair System" button, but that button seems to do nothing useful beyond closing the dialog. The next time I log in, the same "Offline Updates" dialog appears, and it does this every time I log in.

Scanning for error information in /var/log/messages yields (for this particular offline updates failure):

[root]# grep -sri curl | grep -i mirror | grep -i error
messages:Sep 3 22:39:21 vm-f34-home journal[2915]: LRO_METALINKURL processing failed: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metal ... rch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]
messages:Sep 3 22:39:21 vm-f34-home pk-offline-update[2904]: failed to update system: cannot update repo 'fedora': Cannot prepare internal mirrorlist: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metal ... rch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]; Last error: Curl error (6): Couldn't resolve host name for https://mirrors.fedoraproject.org/metal ... rch=x86_64 [Could not resolve host: mirrors.fedoraproject.org]

For what it's worth, when offline updates fails, if I immediately log back in (after the reboot) I can successfully use Fedora's 'dnf' command line utility to install software updates:

[root]# dnf -y upgrade

And yet even after I use dnf to successfully install software updates, every time I log in I get the same Discover "Offline Updates" error message dialog above the system tray. And clicking on the dialog's "Repair System" button does not remedy this; the next time I log in the "Offline Updates" error message dialog pops up above the system tray.

Apparently, PackageKit is the culprit here. I successfully squelched the "Offline Updates" failure message using PackageKit's console client (pkcon):

[root]# pkcon -v -p repair
[root]# pkcon refresh force -c -1 -v -p