/usr/lib/gnu-smalltalk/gst-gtk.so is in libgtk2-gst 3.2.5-1.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gnu-smalltalk/gst-gtk-3.2.5.so
/usr/lib/gnu-smalltalk/gst-gtk-3.2.5.so