Hello! I just spent the past 2 days wrestling with installing jetpack through the sdkmanager and it was not straightforward whatsoever but luckily I was able to combine all my trail and error and research on the forums into a text document with instructions for anyone else who needs help performing the same procedure.
This is what worked for me, I have the J120 rev7 but I believe the rev9 requires an additional modifications to perform the USB port patch.
I can confirm that both the USB ports are operational after performing the steps I outlined in the instructions provided. Let me know if anything is unclear and I will do my best to help you out!
Instructions to install jetpack 4.2 on J120 TX2.txt (5.5 KB)