/usr/lib/x86_64-linux-gnu/libSimTKsimbody.so is in libsimbody-dev 3.5.4+dfsg-1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libSimTKsimbody.so.3.5
/usr/lib/x86_64-linux-gnu/libSimTKsimbody.so.3.5