Talking about libglacierapp:
https://github.com/nemomobile-ux/libglacierapp/blob/master/src/glacierapp.cpp

While it could like qtquickcontrols-nemo depends on it, actually it's not (examples part only).

Library called glacierapp is ~150 lines of cpp wrapper for QGuiApplication, QQmlApplicationEngine and QQuickWindow, that hardcodes QQC1 Style to "Nemo", sets app name and loads translator and main qml file, saving the window position if possible.

The package is provided independently from qtquickcontrols-nemo:

https://github.com/nemomobile/qtquickcontrols-nemo/blob/master/rpm/qtquickcontrols-nemo.spec 
https://github.com/nemomobile-ux/libglacierapp/blob/master/rpm/libglacierapp.spec

Is it makes sense to fix the rpm and alpine packages? To set qtquickcontrols-nemo as a dependency for the libglacierapp, since libglacierapp is asking for qtquickcontrols-nemo, not vise-versa.

There's also LGPLv2 libsailfishapp that is doing approximately the same (but without setting QQC1 style variable, since it was written before qqc1 existed):
https://github.com/sailfishos/libsailfishapp

Looks like it would be nice to merge them someday?

Looking at kirigami approach: kirigami-gallery is not using a separate library for that for now, just adding needed initialization at the main file https://github.com/KDE/kirigami-gallery/blob/master/src/main.cpp