Ubuntu 20.04 on ASUS ZenBook Flip 15 UX562FD-A1086T: Display orientation (unchangably) wrong when external monitor is connected

System & feature description:
The Asus Zenbook laptop has a 360 degree flippable, touchscreen-display with an internal orientation sensor to detect the (upright) orientation of the display (in space). This lets the display orientation always correctly turn upright automatically as long as no additional external monitor is connected. As the orientation of the build-in monitor is automated, no extra "Orientation" drop-down menu is provided in 'settings->display' for it, which is also okay.

Bug:
As soon as an additional external monitor is connected via HDMI, then following bugs are observed:
- The orientation of the build-in monitor falsely (and for not good reason) rotates clockwise by 90 degree even though the laptop is still in normal orientation and was not moved/rotated.
- If you take the laptop and now rotate it by 90 degrees counter-/clockwise, then the rotation only induces a change in resolution (both of built-in & external monitor) but no change in orientation of the build-in monitor is observed.

Comments:
It looks like the orientation-sensor input is not accounted properly/at all for as soon as an external monitor is connected.

Solution:
Integrated orientation sensor input properly when external monitor is connected.

Suggestions:
Instead of no display "Orientation" drop-down menu at all, the standard drop-down list ("Landscape", "Portrait Right", "Portrait Left", "Landscape (flipped)") with an addition choice "Automatic (detected)" could be provided. The default value could be set to "Automatic (detected)".