DIY patch (untested)
sed -i -e 's|lxsession-default-terminal %s|x-terminal-emulator -e %s|' \ /etc/xdg/lubuntu/libfm/libfm.conf
DIY patch (untested)
sed -i -e 's|lxsession- default- terminal %s|x-terminal- emulator -e %s|' \ xdg/lubuntu/ libfm/libfm. conf
/etc/