/usr/lib/x86_64-linux-gnu/libtclmatrixd.so.9 is in plplot-tcl 5.10.0+dfsg2-0.1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libtclmatrixd.so.9.2.0
/usr/lib/x86_64-linux-gnu/libtclmatrixd.so.9.2.0