/usr/lib/x86_64-linux-gnu/libFLAC.so is in libflac-dev 1.3.0-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libFLAC.so.8.3.0
/usr/lib/x86_64-linux-gnu/libFLAC.so.8.3.0