After traumatizing myself even further by installing Windows 11 in a qemu VM, I was able to repeat the successful blinking light demo showing again that the hardware, cable, and blinking light program were all good. This also now exonerates Linux USB handling which Linux happily passed through to the Windows VM.
This shows there is a clear problem with the ESP32 Arduino-IDE Linux tools that is not a problem with the Windows tools.
Why no Serial output ever is observed (even on native Windows) is still a mystery.