/usr/lib/x86_64-linux-gnu/libprotobuf.so.9 is in libprotobuf9v5 2.6.1-1.3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libprotobuf.so.9.0.1
/usr/lib/x86_64-linux-gnu/libprotobuf.so.9.0.1