/usr/lib/libgimpui-2.0.so is in libgimp2.0-dev 2.8.16-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libgimpui-2.0.so.0.800.16
/usr/lib/libgimpui-2.0.so.0.800.16