When running /usr/lib/kscreenlocker_greet --testing I get:
$ /usr/lib/kscreenlocker_greet --testing
Locked at 1656336119
Cannot mix incompatible Qt library (5.15.3) with this library (5.15.5)
Aborted (core dumped)
But reinstalling qt (entire package with subsequent/dependent ones) and kscreenlocker, along with rebuilding qt5-styleplugins (as shown in Screen locker is broken) did not help.
$ lookandfeeltool -a org.manjaro.breath-light.desktop
QDBusConnection: error: could not send signal to service "" path "//home/roman/.kde4/share/config/kdeglobals" interfac
e "org.kde.kconfig.notify" member "ConfigChanged": Invalid object path: //home/roman/.kde4/share/config/kdeglobals
QDBusConnection: error: could not send signal to service "" path "//home/roman/.kde4/share/config/kdeglobals" interfac
e "org.kde.kconfig.notify" member "ConfigChanged": Invalid object path: //home/roman/.kde4/share/config/kdeglobals
QDBusConnection: error: could not send signal to service "" path "//home/roman/.kde4/share/config/kdeglobals" interfac
e "org.kde.kconfig.notify" member "ConfigChanged": Invalid object path: //home/roman/.kde4/share/config/kdeglobals