Hybrid mode: external displays are stuck in landscape mode

[leviport]

Tested on an oryp6 with a 1440p display over mini DisplayPort. Pop 20.10 and 20.04 both seem to be affected.

To reproduce:

1. Switch to Hybrid mode
2. Make sure that you are on NVIDIA 455.38
3. Connect an external monitor (I used a DP to mDP cable, @ahoneybun reports the same behavior over HDMI)
4. Switch the external display to Portrait (it doesn't matter if it is left or right)
5. Watch the external display turn off and the laptop is in Single Display mode in Settings -> Displays

It looks like it keeps trying to detect the external display, but keep reverting to only the built-in display. I suspect it may be related to #61