mini2018 & iGPU + eGPU  

@toke-lahti, You'd need an EFI boot loader to keep the iGPU activated in Windows Boot Camp. I use the modified apple_set_os.efi v0.5 and can drive an ASUS USB-C monitor with the iGPU and other monitors with the eGPU [build link].

@itsage,

Posted by: @aa15032261

4. Connect in your eGPU to a thunderbolt port on the left side then press any key

5. Once Windows is booted, disconnect your eGPU then connect it to a thunderbolt port on the right side

Does this apply to Mini?

Does it matter which port is left to permanent use?

And does this EFI bootloader even work with Mini?

I have both macos and win10 installed in a separate external drive.
Should I really edit the boot-file in macos disk?

@toke-lahti, It complicates things when you have Windows and macOS on separate volumes. The modified apple_set_os.efi v0.5 solution uses the EFI volume on the macOS partition. I would say to use Windows 10 1903 V1 and hot-plug the eGPU for your setup.

Well, simple things like one-volume-for-one-OS seems to be so hard these days.

One volume for one homedir did not work for macos either.

(Initially I thought my mini's small soldered ssd could house the OS and speed hungry apps and the homedir and less hungry apps would be on external not-so-fast ssd.)

Maybe I'll start to install macos to every storage drive I have, then there should be a whole less problems...

Because, why not?

I'd take my win10 drive, wipe it clean, format as apfs, install macos and then use normal supported bootcamp and all the troubles are away?

Or, is there problems with eGPU's with "normal" bootcamp installation?

@itsage, if I remember correctly, I'm ahead of 1903 already.

But, would the "HackFlags 0x600"-trick work with hotplug and RX580?