/usr/lib/x86_64-linux-gnu/libfm-gtk.so is in libfm-gtk-dev 1.2.4-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libfm-gtk.so.4.0.4
/usr/lib/x86_64-linux-gnu/libfm-gtk.so.4.0.4