/usr/lib/x86_64-linux-gnu/libotr.so is in libotr5-dev 4.1.1-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libotr.so.5.1.1
/usr/lib/x86_64-linux-gnu/libotr.so.5.1.1