I have 2018 mac mini, just bought it a few days ago, running OS X Mojave. And I have 2 monitors connected to it, 1 through usb-c and 1 through HDMI.
Whenever I wake my computer up from sleep, the monitor connected through usb-c wakes up instantly, but the other one takes a while to wake up. Like I could already be using the left screen and the right one is still black.
I tried plugging a different display to this HDMI port and it's the same story, the monitor takes like 1 minute to start displaying the picture, after I wake my computer from sleep, but, this other monitor instead of just being a black screen displays white noise and then wakes up.
What could be the problem?
Best Answer
There are lots of reports of monitor problems with the 2018 Mini: so many that it seems unlikely to be anything other than a problem with the hardware itself (or specific firmware/software to that model).
I myself see the same problem: white noise on the HDMI-connected monitor after Sleep.
Using 2 TB/USB-c ports rather than one TB/USB-C and one HDMI may be a factor, rather than the cable itself.
It's unknown at this stage whether Apple may be able to fix it (with enough bug reports) in a software update, or whether it's a permanent hardware issue.