/usr/lib/x86_64-linux-gnu/libserd-0.so is in libserd-dev 0.18.2~dfsg0-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libserd-0.so.0.18.2
/usr/lib/x86_64-linux-gnu/libserd-0.so.0.18.2