/usr/lib/x86_64-linux-gnu/libdebian-installer.so is in libdebian-installer4-dev 0.88ubuntu4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdebian-installer.so.4.0.7
/usr/lib/x86_64-linux-gnu/libdebian-installer.so.4.0.7