I've reached the limit (very quickly) of my capabilities in terms of hardware trouble-shooting. I thought because the rest of the fans and everything seemed to be making the customary sounds and LED lights were flickering... all except for the monitor wasn't coming on: that the graphics card had finally given up the ghost. However, replacing the graphics card did nothing: things still hum and the monitor still doesn't come on, although it does when connected to other PCs. So... MB? No clue.

Going to take it in tomorrow to people with infinitely more knowledge than I have about this sort of thing and let it become their concern.

Thank you all for your kind consideration of my strange little conundrum.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks