My re-re-re…installation was fine (the culprit was a faulty USB cable from a ST Micro development kit, handed out by ST Applications Engineers at the ST Day conference in Seattle), here are the steps and pitfalls:
(1) Please follow the install instructions exactly as per https://github.com/erwango/openocd-stm32.
(2) Don’t follow the steps on either https://www.zephyrproject.org/doc/getting_started/installation_linux.html OR
(3) Use a KNOWN good USB to USB micro cable!
(4) You may need correct arm-gcc and arm-gdb; let Debian’s “Synaptics Package Manager” and Fedora’s “Yum Package manager” point the correct dependencies.
(5) If possible, sit next to Peter (Thank you Peter!) who helped a ton!
(6) To flash to STMicro board, use the command:
stm32_flsh l4 ~zephyr/samples/hello_world/outdir/disco_l475_iot1/zephyr.bin
Wait for ST Micro flash to be written, you may get a message such as “Unable to match requested speed 500 kHz, using 480 kHz” (not an error)
(7) Set screen communication (or use Arduino IDE to see the output):
screen /dev/ttyACM0 115200 (else you may see garbage outputted by ST Micro board)
(8) Press the “RESET” button on the ST Micro board and see “Hello World” in the terminal (screen)!