/usr/lib/x86_64-linux-gnu/libsss_idmap.so.0 is in libsss-idmap0 1.16.1-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libsss_idmap.so.0.5.1
/usr/lib/x86_64-linux-gnu/libsss_idmap.so.0.5.1