Sketch is compiled with Arduino IDE and I use this command to flash Nano with avrdrude and the usbtiny programmer (booltloader still present after):
$ avrdude -c usbtiny -p m328p -U flash:w:/tmp/builda567167170c1a05374041e7440986765.tmp/DigitalReadSerial.ino.with_bootloader.hex
In this sketch I do a blinky led and write on serial port. I can received caracter after falshing.
For the cable, it's a very short cable and work fine with a another Arduino Nano (no CH341 driver).
thanks,