Hi,
I managed to make it work using a nano motorboard. I’m using windows machine and managed to write hex file using AVRDUDESS. Here’s how it works:
First plug your nano to computer using a usb cable then open device manager and find its port.
Then open avrdudess set programmer to arduino (green highlight), from presets select arduino nano (blue highlight), from port select your com which you found from device manager (red highlight), set baud rate to 115200 (yellow highlight), select nano.hex file (purple highlight), and hit program.
As you can see from screenshot it worked.
Bonus:
Openflexure connect detection:
New gui:
Thanks for providing hex files.