/usr/lib/x86_64-linux-gnu/libpmix.so.2.1.3 is in libpmix2 2.1.1~rc1-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/pmix/lib/libpmix.so.2.1.3
/usr/lib/x86_64-linux-gnu/pmix/lib/libpmix.so.2.1.3