The same update that caused my screen to go blank shortly after logging in also caused the fingerprint reader to fail to unlock my screen. It turns out the two problems were completely unrelated. The first was a hardware problem that was simply revealed by a new kernel and went away when I put a new display in my machine (I think).
The fingerprint unlock problem, as it turns out, was due to an obscure change in Qt that (intermittently) affected everyone running the latest Plasma Desktop (6.3.4) and using a fingerprint reader to unlock their screen. There was a patch posted for a related issue that resolves this one as well:
109a110
> property bool ignorePositionChanged: true
121c122,125
< onPositionChanged: uiVisible = true;
---
> onPositionChanged: {
> uiVisible = !ignorePositionChanged;
> ignorePositionChanged = false;
> }
You need to apply the patch to the LockScreenUi.gml file. Its location might vary; on Fedora 41 the commands to use are:
First, back up the original file:
sudo cp -p \
/usr/share/plasma/shells/org.kde.plasma.desktop/contents/lockscreen/LockScreenUi.qml \
/usr/share/plasma/shells/org.kde.plasma.desktop/contents/lockscreen/LockScreenUi.qml.bak
Then run this command and copy/paste the patch above, followed by ^D.
sudo patch /usr/share/plasma/shells/org.kde.plasma.desktop/contents/lockscreen/LockScreenUi.qml
If this looks like gibberish to you, then you probably should just wait until the fix gets incorporated into the next KDE Plasma desktop release. Patching system files can cause all manner of headaches if you mess it up.
—2p