Can't set external monitor as main
 

I have my desktop extended across a laptop (1) and an external monitor (2) connected through DisplayLink.

When I use display settings in control panel to set 2 as the primary monitor, the display resets but leaves 1 as the primary. i.e. It does nothing.

If I use "Notebook Monitor Off" in the DisplayLink, then 2 becomes the primary as expected. However, if I then use "Set as Main Monitor" or any of the "Extend" options, I end up with 1 as the primary again...

No matter what I do, I am stuck with the laptop as primary. Any fix?