/usr/include/linbox/matrix/ is in liblinbox-dev 1.3.2-1.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/linbox/matrix/archetype.h
/usr/include/linbox/matrix/blas-matrix-multimod.h
/usr/include/linbox/matrix/blas-matrix.h
/usr/include/linbox/matrix/blas-matrix.inl
/usr/include/linbox/matrix/blas-submatrix.inl
/usr/include/linbox/matrix/blas-triangularmatrix.inl
/usr/include/linbox/matrix/dense-rows-matrix.h
/usr/include/linbox/matrix/factorized-matrix.h
/usr/include/linbox/matrix/factorized-matrix.inl
/usr/include/linbox/matrix/matrix-category.h
/usr/include/linbox/matrix/matrix-domain-gf2.h
/usr/include/linbox/matrix/matrix-domain.h
/usr/include/linbox/matrix/matrix-domain.inl
/usr/include/linbox/matrix/permutation-matrix.h
/usr/include/linbox/matrix/permutation-matrix.inl
/usr/include/linbox/matrix/random-matrix.h
/usr/include/linbox/matrix/random-matrix.inl
/usr/include/linbox/matrix/sparse.h
/usr/include/linbox/matrix/sparse.inl
/usr/include/linbox/matrix/transpose-matrix.h