I finally got it working, Optimus + eGPU to power the dGPU Macbook internal display.    There's a slight performance impact from using Optimus, but that's to be expected.      reFit/apple_set_os.efi to enable Iris gpu-switch (integrated.bat) to select the iGPU / reboot install the iGPU drivers and run integrated.bat / shutdown -- connect eGPU and boot you should have 3 devices in Device Manager, with the eGPU showing an err