2018 Mac Mini [8th,6C,B] + RX Vega 56 @ 32Gbps-TB3 (Razer Core X) + macOS 10.14.6 & Win10 [mesocyclone]
Late 2018 Mac Mini, 16GB RAM, 500GB SSD, Core I7 3.2Ghz, Intel UHD Graphics 630 iGPU, Mac OS X 10.4.6 and Windows 10 1809 in Bootcamp.
Will add later.
For Mac OS X installation was entirely plug and play. I haven't really had any issues using the eGPU in native Mac OS aside from a couple of crashes and one kernel panic that thus far seem unrelated to the eGPU (kernel panic happened during sleep, which apparently is a known issue related to T2 chip that thankfully has not repeated itself).
For Windows 10 in Bootcamp, the installation was, predictably, problematic and extremely hacky. Initially I installed the available Windows 1903 ISO which, if you are getting it for the first time currently, is build .356. I was able to install Radeon drivers by powering on the eGPU in Windows, but ultimately couldn't solve error 12 and couldn't boot into windows with the eGPU plugged in even via automateEFI bootloader without getting a frozen Windows logo and flickering green screen.
I reinstalled the other Win 10 ISO currently available via Microsoft which is version 1809. I decided to try this build without updating and followed very closely these instructions. The only step I altered was in getting Windows to detect the card initially. I wasn't able to boot into the Windows partition with the eGPU powered on without getting the frozen logo/green screen, so I powered the eGPU while in Windows, removed it from Device Manager, rebooted, repeated the process until Generic Display Device was shown in Device Manager in Windows.
I then installed the Radeon drivers and rebooted with the eGPU plugged in and powered, but encountered the logo/flicker problem again. I believe I had to power cycle the Mini a couple more times before something changed and Windows froze at the login instead. One more reboot and Windows loaded with the eGPU recognized. It was a lot of frustrating trial and error during which I often cursed Windows and the money I spent on the license key. Note that I was doing this at all times using automateEFI boot partition on a thumb drive and the monitor's HDMI cable plugged into the Mini.
During this process a few times as well, my (older, Apple USB-A) keyboard ceased to be recognized booting back into Mac OS seemingly at random. A further curiosity and one I've read about elsewhere is that the Mini's power LED ceases to function after a boot into Windows until the computer is shut down completely and restarted into Mac OS.
After this final boot, the eGPU has been functioning in Windows for all of one day, so we'll see if it stays that way! I'd like to update Windows to the recommended 1903 build .295, but since I don't know which standalone installer(s) will bring it up to 1903 I've decided to just keep the version I have. Maybe I've missed some method of creating a custom versioned ISO, or a clear way to upgrade from 1809 .xxx to 1903 .295, but that's where I'm at.
As a small edit, I realized after reading through a couple of other build threads that the automateEFI boot might not be needed with the Mini. Enabling the integrated GPU is mainly for using two monitors and for being able to see what you're doing while setting up the eGPU in Windows. After having some weird issues with Windows randomly forgetting about the eGPU on bootup, I have tried instead setting the preferred boot sector to Bootcamp in Mac OS X, connecting and powering on eGPU with monitor attached directly to eGPU port, and restarting into Windows without the bootloader. So far it has worked much more reliably than keeping the iGPU enabled.
Will update post with them.
At this point I have to just accept that I got the eGPU entirely for gaming. On purchase, I figured I would just need it in general because of the underpowered iGPU in the Mini, but when not gaming I've never had an issue using the UHD 630. However, since playing even old AAA releases and even Minecraft with shaders and high graphics settings is impossible with the iGPU, the Vega has been great. Interestingly and perhaps unsurprisingly, Windows games that have been ported into Mac OS, e.g. games that use Wine/Wineskin wrappers, seem much more resource intensive than their Windows counterparts. I've installed Witcher 3 in Bootcamp and it appears to stress the system much less so far, although I haven't really pushed it at max settings much. Not specifically eGPU related, a problem with gaming in Bootcamp is that the T2 security chip prevents the use of a fan control, without which the Mini seems to like to regularly push the CPU past 90C with absolutely no increase in fan RPM. Apparently a workaround is to set the fan to a constant speed via something like macsFanControl in Mac OS, then reboot into Windows.
All in all, I'm now happy with my setup and have hopefully taken adequate measures to keep it working for now until newer OS updates of both flavors stop breaking eGPU compatibility.
After this final boot, the eGPU has been functioning in Windows for all of one day, so we'll see if it stays that way! I'd like to update Windows to the recommended 1903 build .295, but since I don't know which standalone installer(s) will bring it up to 1903 I've decided to just keep the version I have
When I updated from 1803 to 1903 (using Windows Update), I got build 418 but was able to uninstall that to get build 1, and then manually installed 295.