I used an NVIDIA Surround Display and 2 WinWing MFDs for my F18 for a very long time. I have completely filled 2 16-port hubs and an 8-port hub for my home cockpit. The first two USB displays are connected to the same HUB and Win11 remembers the orientation. When I plugged the third USB display into the same HUB, ALL USB displays were always reset to landscape. Even when I had them in portrait mode and only jumped out of DCS with ALT TAB! Plugging from one 16-port HUB to another 16-port HUB caused another strange behavior.
Here, the last activated USB display was always kept in landscape mode and the other two remained in portrait mode. WTF Windows?!!!?
The checkbox in WinWing's SIMAPPPRO that is supposed to set the orientation only works once at boot time. After that the Display jumps back to the Windows setting!
Solution:
Try out on which USB HUB and port the displays are ALL retained. I now have the third display on the 8-port HUB and Win11 remembers the orientation cleanly and it now stays that way in DCS.