The ASUS ProArt Display monitors seem to suffer from intermittent resets, which turn the screen dark for a second or two. Sometimes, the glitch happens in quick successions or a few times a day, but it can also be whole days in between manifestations.
When replacing the signal cable, connecting the monitor to different computers, turning some of its features off, updating drivers for the operating system, etc. do not fix the malfunction, the following think-outside-the-box solution could work.
Loosen the power supply plug going into the back of the monitor. Intuition suggests that the tighter it is fitted, the more secure the electrical contacts are and the less likely it is that the monitor will lose power and suffer resets. In the case of the ASUS ProArt Display monitor, it appears that the opposite is true: if the plug is pushed in too tight, the monitor will glitch.
From my web searches, I saw a few forum posts hinting at faulty power cables, but I initially discarded the idea because the monitor uses a bog-standard power cable that has very little that can be faulty. After I exhausted all other possibilities, I had only the fix described above to try. And it worked.