/usr/include/singular/singular/kernel/GBEngine/ is in libsingular4-dev-common 1:4.1.0-p3+ds-2build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/singular/singular/kernel/GBEngine/f5c.h
/usr/include/singular/singular/kernel/GBEngine/f5data.h
/usr/include/singular/singular/kernel/GBEngine/f5gb.h
/usr/include/singular/singular/kernel/GBEngine/f5lists.h
/usr/include/singular/singular/kernel/GBEngine/janet.h
/usr/include/singular/singular/kernel/GBEngine/kInline.h
/usr/include/singular/singular/kernel/GBEngine/khstd.h
/usr/include/singular/singular/kernel/GBEngine/kstd1.h
/usr/include/singular/singular/kernel/GBEngine/kstdfac.h
/usr/include/singular/singular/kernel/GBEngine/kutil.h
/usr/include/singular/singular/kernel/GBEngine/nc.h
/usr/include/singular/singular/kernel/GBEngine/ratgring.h
/usr/include/singular/singular/kernel/GBEngine/ringgb.h
/usr/include/singular/singular/kernel/GBEngine/shiftgb.h
/usr/include/singular/singular/kernel/GBEngine/syz.h
/usr/include/singular/singular/kernel/GBEngine/tgb.h
/usr/include/singular/singular/kernel/GBEngine/tgb_internal.h
/usr/include/singular/singular/kernel/GBEngine/tgbgauss.h
/usr/include/singular/singular/kernel/GBEngine/units.h