/usr/lib/x86_64-linux-gnu/libLinearMath.so is in libbullet-dev 2.82-r2704+dfsg-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libLinearMath.so.2.82
/usr/lib/x86_64-linux-gnu/libLinearMath.so.2.82