Here’s something a bit longer regarding serial console:
https://forums.developer.nvidia.com/t/changing-kernel-configurations-in-clonned-image/226150/13
The gist is that you use a micro-B USB cable from the Jetson to a host PC. Then you attach to the device which shows up (typically “/dev/ttyACM0”) at speed 115200, 8 bits, no parity, and 1 stop bit (115200 8N1). I like gtkterm as a serial console program (“sudo apt-get install gtkterm”). That other URL mentions using that for connecting.
The serial console program will allow you to clear the screen (if you’ve been booting for test), start logging, and then when you turn on the Jetson it should log everything. The log will be on the host PC and you can attach it to the forum.