What you could try is to use my created live image.

- run flasher -i
- connect the switched off N9 via usb

and tell us if you get an output.
When you get no output terminate with ctrl+c.
Look with the command dmesg if some usb device was recognized.

When no device was recognized maybe your cable is broken, your N9 is broken or the usb port is not running with free linux drivers.

You could try to use another pc maybe an older one.

When you phone was recognized you can try to flash it.
However I am not responsible for anything if something unexpected happens..