I also see the same list of errors from sddm-greeter using the default
KDE/Plasma Breeze theme on Bullseye.
I'm not familiar with the KDE/Plasma QML theme system but I believe I've
found a clue/cause.
Almost all the errors are related to units.XXX but units isn't available
and evaluates to NULL.
This KDE page indicates "units.XXX" are a Plasma component/class:
https://develop.kde.org/hig/layout/units/
My hypothesis is that sddm-greeter is not finding/importing the file
that defines the 'units' class/component whereas when a full Plasma
session is operating this class/component is implicitly expected to be
available.
The solution may be as simple as an additional (conditional) import
statement.
On the host I see several possible sources for it:
$ dpkg -S Units.qml
plasma-framework:
/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/styles/org.kde.desktop.plasma/Units.qml
qml-module-org-kde-kirigami2:
/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/Units.qml
qml-module-org-kde-kirigami2:
/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/styles/org.kde.desktop/Units.qml
plasma-framework:
/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/styles/Plasma/Units.qml
The first of these looks likely to be the required definition (on the
basis it contains some 'readonly' properties) but I'm not sure how the
path would be converted to a correct 'import' statement:
/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/kirigami.2/styles/org.kde.desktop.plasma/Units.qml
However it may be it should be imported via another dependency.
