Thank you for the link. I imagined there would be little to be done without more information.
Curiously, after going through setup on another debian build, I decided to give the stretch img another shot, and now it seems to be working.
The only thing different is, it is being powered by a USB cable not from a simple power supply, but from a PC (and recognized as PI USB to serial )No idea if that is relevant, but it seems to be working now.