I have an external USB C monitor I wanted to use in portrait orientation to read PDFs and articles. DEX seems to have no option for portrait mode.
Screen mirroring doesn't actually change the orientation if the phone is in portrait mode. It just shows the portrait image smaller and in the centre of a landscape oriented image (same as it would behave with a TV). I can't find any option to change this. I tried a few apps and they all end up with the same behavior. It seems shocking at this point that you can't get an external display to work in portrait mode with android. If anyone has suggestions, please let me know.