Any update on this? I've tried the same process as @Gaurav-Borade, including the instructions here:
Page not found
ModalAI technical documentation for VOXL and VOXL 2 Companion Computers for PX4 and ArduPilot Obstacle Avoidance and GPS-denied navigation, assembled in the USA
ModalAI Technical Docs (docs.modalai.com)
and I also see nothing listed under sudo fastboot devices.
Using the usb-expander-and-debug-user-guide I'm able to start a screen to /dev/ttyUSB0, but I can't get adb shell to work after the screen is started.
I'm on Ubuntu Linux 18.04, I'll switch to another Ubuntu 18.04 machine and re-run the debricking procedure to see if anything changes.