/usr/lib/libatm.so is in libatm1-dev 1:2.5.1-1.5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libatm.so.1.0.0
/lib/x86_64-linux-gnu/libatm.so.1.0.0