I’ve been following this thread because I have a UP2715K, albeit am using an Intel Mac Mini at the moment. Even with that setup, I’ve found that the monitor is sensitive to cables. I purchased 8k compatible DP1.4 cables, which seem to do the trick. And my adapter is a Thunderbolt to dual DP adapter… I’m not at my computer at the moment, but I can dig up the exact model if you like. However, I purchased a few different ones, and all work.
I am connecting my Mac to the adapter through a Caldigit Ts3+ Thunderbolt dock.
Now for the flakiness and my work arounds:
1. I’ve never been able to boot directly in 5K. I have to disconnect one DP cable, reboot, and then once MacOS starts, plug in the other one. To make this process easier, I bought a passive DP A/B switch. I press a button to go down to one DP cable, reboot, and then press the button again once MacOS has loaded.
2. My computer never sleeps, but the display does turn off. At times it won’t wake. I have to cut power to the monitor (not just turn it on and off…literally pull the cord)l and the reapply and the monitor will wake. To automate this, I have the monitor on a remote controlled outlet… when it doesn’t wake, I turn off the monitor by pressing a button, wait a few seconds, and then turn on.
With these two works arounds, the monitor has been flawless. I discovered them back when I was running the display off a Mac Pro 2013 (trash can), so it’s not an issue of the Mac Mini.
for the 8k cables, I use these:
This DisplayPort 1.4 cable lets you connect your DP laptop or desktop computer to an ultra-high definition 8K monitor, TV or projector. The DP monitor cable provides the essential final link in your audio-video setups and is ideal for: Delivering enriched presentations; Displaying crisp digital s...
smile.amazon.com
A 3m cable from one port directly to the monitor. A 1m cable from the other to the a/b switch, and then a 2m cable from the switch to the monitor.