LinuxQuestions.org - Debugging hibernation on laptop without a serial port

I'm not sure that I'm posting in the correct topic. I chose hardware because my question currently revolves around USB/Serial devices. Please let me know if I should post this somewhere else.

I have a System76 Galago Pro laptop that I bought last summer. I have recently completed a Linux From Scratch build on it and have been playing around with various kernel features trying to learn how to use them. I briefly had hibernation working properly on the laptop, but it has now stopped functioning entirely. When I run
echo disk | sudo tee /sys/power/state
(which once worked as the command to initiate hibernation) the system pauses userspace programs, then the screen corrupts (graphics driver's fault?) and the system hangs. I can hold the power button to turn it off and restart, but the hibernation failed.

I'd like to diagnose the problem. I sometimes see flashes of kernel errors and warnings on the system console during this process, but I can't read anything before they disappear. Because userspace is not running when the system is creating a hibernation image, the logging daemon is not writing the kernel log to disk. I have no record of the error messages at all when I reboot.

I think this is the kind of problem that would be debugged by hooking up a serial terminal and setting the kernel to use that serial TTY as the system console. I do not have a hardware serial terminal or really any serial devices at all, just USB. I do, however, have multiple laptops at my disposal. So I guess I have several questions:

Does anyone know of a non-serial way that I can persist a copy of the logs while userspace is suspended?
Is there a way to connect two laptops (usb or ethernet cables?) and use one as a serial terminal for the other?
Do I need to buy two usb-to-serial converters and connect my two laptops so that they both just see a serial connection?

Thanks!