/usr/lib/x86_64-linux-gnu/libmatio.so is in libmatio-dev 1.5.9-1+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmatio.so.4.2.0
/usr/lib/x86_64-linux-gnu/libmatio.so.4.2.0