/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/ is in qtmultimedia5-dev 5.9.5-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QCameraViewfinder
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QGraphicsVideoItem
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QVideoWidget
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QVideoWidgetControl
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QtMultimediaWidgets
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QtMultimediaWidgetsDepends
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/QtMultimediaWidgetsVersion
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/qcameraviewfinder.h
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/qgraphicsvideoitem.h
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/qtmultimediawidgetdefs.h
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/qtmultimediawidgetsversion.h
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/qvideowidget.h
/usr/include/x86_64-linux-gnu/qt5/QtMultimediaWidgets/qvideowidgetcontrol.h