Comment 12 for bug 1768294

Actually `eject` is a standard part of the install and doesn't even require the device name. Obviously if there's more than one device and you want to open one over the other, it needs to be specific, but there's always a default device. That said, the solution is fairly easy:

 1. Open up ~/.config/openbox/lubuntu-rc.xml in an editor
 2. Go to either the beginning or ending of the <keyboard> section
 3. Add this:

  <keybind key="XF86Eject">
    <action name="Execute">
      <command>eject</command>
    </action>
  </keybind>

 4. Save and restart openbox with `openbox --reconfigure`

I'll add this to a future version of lubuntu-default-settings, but you can do that in the meanwhile.