/usr/include/libsyncdaemon-1.0/libsyncdaemon/ is in libsyncdaemon-1.0-dev 3.0.0-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libsyncdaemon-1.0/libsyncdaemon/libsyncdaemon.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-authentication.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-config-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-credentials.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-daemon.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-events-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-file-info.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-filesystem-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-folder-info.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-folders-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-metadata.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-publicfiles-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-share-info.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-shares-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-status-info.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-status-interface.h
/usr/include/libsyncdaemon-1.0/libsyncdaemon/syncdaemon-transfer-info.h