Mac mini 2018 will not wake screen (deliver video) after sleep after Monterey 12.3

My Mac mini 2018 has always been connected to my LG27UK850 UHD display with a USB-C cable and it has, until now, worked perfectly.

After updating Monterey to 12.3, once the display has turned off, or sleep has been invoked, when I hit the esc key, the monitor wakes up, but there is no video from the Mac, and I am forced to power off the Mac and start again.

I have tried resetting Energy Saver prefs to default values, also tried "Prevent your Mac from automatically sleeping" and all combinations with that and "Put hard disks to sleep ..." (probably irrelevant with SSD?).

What I have discovered is that if I used an HDMI cable, the problem doesn't occur. I initially used the first cable to hand but when I noticed that very fine text (e.g. Little Snitch display in menu bar) was no longer crisp I tried using the high quality HDMI cable that came with the monitor. This considerably improved the text, but still it was not as good as it was via USB-C.

I also discovered a mountain of posts in various forums, including this, on this apparently insoluble problem with Mac minis (although it seems most people have issues with non-waking with HDMI connections. I guess I'm lucky I don't have that. Yet. Monterey 12.4 maybe?