Flashing GDO white v1 stuck at "Preparing Installation"

Trying to reflash my GDO white v1 to finally get it working and it is stuck on “Preparing Installation”.

I’ve tried multiple different USB cables.

I had this exact issue. For me, it was the USB cable. Apparently most MicroUSB cables I had lying around were power-only.

FYI - when it works, it’s almost instant.