Thank you, that is good information to know. In fact I just tested it and indeed, the robot shutdown okay with PCI mode.
One final thing to note is that during boot of the image ISO, before the Ubuntu installation, I saw 4 or 5 lines of warnings relating to ACPI. Sorry I did not take photo soon enough. I do not remember seeing those warnings when BIOS eMMC support was set to ACPI.
Otherwise the image appears to have installed correctly.
Thank you and kind regards,