xrandr --output HDMI1 --auto --rotate left --output HDMI2 --auto --rotate left --right-of HDMI1 --output HDMI3 --auto --rotate left --right-of HDMI2
and then go back to the Display Settings, it shows the correct alignment. So the settings program obviously understands the desired final state, but the user has no way to get there (apart from using the command line).
The weird thing about this is if I do:
xrandr --output HDMI1 --auto --rotate left --output HDMI2 --auto --rotate left --right-of HDMI1 --output HDMI3 --auto --rotate left --right-of HDMI2
and then go back to the Display Settings, it shows the correct alignment. So the settings program obviously understands the desired final state, but the user has no way to get there (apart from using the command line).