/usr/include/ is in libkf5iconthemes-dev 5.44.0-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/
/usr/include/KF5/KIconThemes/
/usr/include/KF5/KIconThemes/KIconButton
/usr/include/KF5/KIconThemes/KIconDialog
/usr/include/KF5/KIconThemes/KIconEffect
/usr/include/KF5/KIconThemes/KIconEngine
/usr/include/KF5/KIconThemes/KIconLoader
/usr/include/KF5/KIconThemes/KIconTheme
/usr/include/KF5/KIconThemes/kiconbutton.h
/usr/include/KF5/KIconThemes/kicondialog.h
/usr/include/KF5/KIconThemes/kiconeffect.h
/usr/include/KF5/KIconThemes/kiconengine.h
/usr/include/KF5/KIconThemes/kiconloader.h
/usr/include/KF5/KIconThemes/kicontheme.h
/usr/include/KF5/KIconThemes/kiconthemes_export.h
/usr/include/KF5/kiconthemes_version.h