/usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/solid/qmldir is in qml-module-org-kde-solid 5.28.0-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | module org.kde.solid
plugin solidextensionplugin
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