/usr/lib/x86_64-linux-gnu/libXxf86dga.so is in libxxf86dga-dev 2:1.1.4-1+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libXxf86dga.so.1.0.0
/usr/lib/x86_64-linux-gnu/libXxf86dga.so.1.0.0