/usr/include/KF5/Solid/solid/ is in libkf5solid-dev 5.18.0-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/Solid/solid/battery.h
/usr/include/KF5/Solid/solid/block.h
/usr/include/KF5/Solid/solid/camera.h
/usr/include/KF5/Solid/solid/device.h
/usr/include/KF5/Solid/solid/deviceinterface.h
/usr/include/KF5/Solid/solid/devicenotifier.h
/usr/include/KF5/Solid/solid/genericinterface.h
/usr/include/KF5/Solid/solid/networkshare.h
/usr/include/KF5/Solid/solid/opticaldisc.h
/usr/include/KF5/Solid/solid/opticaldrive.h
/usr/include/KF5/Solid/solid/portablemediaplayer.h
/usr/include/KF5/Solid/solid/predicate.h
/usr/include/KF5/Solid/solid/processor.h
/usr/include/KF5/Solid/solid/solid_export.h
/usr/include/KF5/Solid/solid/solidnamespace.h
/usr/include/KF5/Solid/solid/storageaccess.h
/usr/include/KF5/Solid/solid/storagedrive.h
/usr/include/KF5/Solid/solid/storagevolume.h