Mac Mini (2018) No Display after a reboot or coming from a shutdown
I started having this black screen symptom this week, after upgrading my 2018 Mini to 10.14.6. Also, frequent kernel panics when the Mac sleeps. Reinstalling OS X (using HDMI) didn't help.
Today I found this buried on Sonnet's eGFX support site:
Under macOS 10.14.6 (but not 10.14.5) or 10.15.4-, a 2018 Mac mini must be booted with a monitor connected to the Mac mini's HDMI port. The monitor may be moved to the GPU after booting. We have filed a bug report with Apple and expect a fix soon.
Not clear whether this would effect other eGPU enclosures as well.
So anyone having this problem only recently, this might be the cause.
It happens if you upgrade or update MacOS or apply a security fix with the eGPU connected to the Mini. All MacOs updates need to be carried out with the eGPU disconnected and the monitor connected to the Mini or eGPU disconnected if connected to a laptop or unit with a screen
This is just one data point, but I haven't had a problem updating Mac OS X 10.14.x over the last year with the eGPU attached. I will avoid doing it going forward though.
Update: Sonnet had changed the wording on the support page to make it clear that this is only an issue when using FileVault. Unrelated to the crashes I've been getting.
I've had a similar situation with a Razer Core X box and a AMD Radeon RV Vega 56. When I first set everything up it was working like a dream until I updated to Catalina. Ever since that update I've had crashes, black screens on restart/reboot. Never ending problems. In the end I shelved the Mac mini and resorted back to using my MacBook Pro. My MacBook Pro never had an issues with the EGPU so I continued to work with this set-up. After a few Catalina updates, I figured Apple would have resolved this issue, so I reconnected the EGPU back to my Mac Mini, but the problem still exists. Super frustrating because I have 64GB of memory on that Mac mini vs only 16 on my MacBook Pro.
I saw someone mention that if you reinstall your OS with a direct connection to a monitor it will resolve the issue. I had zero desire to reinstall my OS...such a huge undertaking, even when all my content is on Time Machine and Dropbox. I tried virtually everything with zero luck, except one.
So, how I resolved my problem was I connected one of my 27" monitors directly into the Mac mini and the other through the EGPU. It's not the best solution because one of the monitors is still getting powered by the shitty Intel UHD 630, but at least my main monitor is getting powered by the EGPU. Since I have made this switch I have not had any issues with crashes nor black screens on restart/reboot.