/usr/lib/x86_64-linux-gnu/libargon2.so is in libargon2-0-dev 0~20161029-1.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libargon2.so.0
/usr/lib/x86_64-linux-gnu/libargon2.so.0