/usr/lib/libreoffice/program/gnome-open-url is in libreoffice-gnome 1:5.1.2-0ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 | #!/bin/sh
# use xdg-open or gnome-open if available, falling back to our own open-url
xdg-open "$1" 2>/dev/null || gnome-open "$1" 2>/dev/null || `dirname "$0"`/open-url "$1" 2>/dev/null
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