There's a key, one of the function keys, I
believe, that has a little
icon of a monitor above it. If you hold down the "fn" key in the lower
left of the keyboard and repeatedly press the other key, you will
toggle between LCD only, LCD and external, and external only.
Fn+F7 (&F3)
I've been trying that. So... My free system may indeed be broken.
or a hook is missing in the OS, if that function needs to operate at
that level.
John A.