/usr/lib/libpanel-applet.so is in libpanel-applet-dev 1:3.26.0-1ubuntu5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libpanel-applet.so.3.0.0
/usr/lib/libpanel-applet.so.3.0.0