Hi,
Whenever I plug anything into the iGPU it seems to become the primary GPU on a system level. When this happens the sensor panel cannot detect the Dedicated Memory of the dGPU. I haven't found a way to change which GPU it reads from. It is not a driver issue as both the A770 and U770 use the exact same driver. It is also convenient using the iGPU for the Sensor panel display.
With nothing plugged into the iGPU
With a display plugged into the iGPU