/usr/include/KF5/KNewStuff3/ is in libkf5newstuff-dev 5.18.0-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/KNewStuff3/KNS3/
/usr/include/KF5/KNewStuff3/KNS3/Button
/usr/include/KF5/KNewStuff3/KNS3/DownloadDialog
/usr/include/KF5/KNewStuff3/KNS3/DownloadManager
/usr/include/KF5/KNewStuff3/KNS3/DownloadWidget
/usr/include/KF5/KNewStuff3/KNS3/Entry
/usr/include/KF5/KNewStuff3/KNS3/KMoreTools
/usr/include/KF5/KNewStuff3/KNS3/KMoreToolsMenuFactory
/usr/include/KF5/KNewStuff3/KNS3/KMoreToolsPresets
/usr/include/KF5/KNewStuff3/KNS3/UploadDialog
/usr/include/KF5/KNewStuff3/kns3/
/usr/include/KF5/KNewStuff3/kns3/button.h
/usr/include/KF5/KNewStuff3/kns3/downloaddialog.h
/usr/include/KF5/KNewStuff3/kns3/downloadmanager.h
/usr/include/KF5/KNewStuff3/kns3/downloadwidget.h
/usr/include/KF5/KNewStuff3/kns3/entry.h
/usr/include/KF5/KNewStuff3/kns3/kmoretools.h
/usr/include/KF5/KNewStuff3/kns3/kmoretoolsmenufactory.h
/usr/include/KF5/KNewStuff3/kns3/kmoretoolspresets.h
/usr/include/KF5/KNewStuff3/kns3/knewstuff_export.h
/usr/include/KF5/KNewStuff3/kns3/knewstuffaction.h
/usr/include/KF5/KNewStuff3/kns3/uploaddialog.h