/usr/lib/x86_64-linux-gnu/libKF5SonnetUi.so is in libkf5sonnet-dev 5.28.0-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libKF5SonnetUi.so.5
/usr/lib/x86_64-linux-gnu/libKF5SonnetUi.so.5