For someone who isn't experienced in how Linux crashes - what currently happens when there's an error that can't be recovered from? Does the device just restart?
A kernel panic handler writes down a piece of stack, a piece of code, contents of registers, and some minimal message.
Normally the machine does not reboot, so that you could photograph the console maybe.
(The screen normally remains white on black. The console can as well be a COM port.)
You can configure it to auto-reboot by putting a timeout value to /proc/sys/kernel/panic.
I don't see why the handler could not go back to textual mode is the console is serial.
Some devices have neither a serial console nor a text-mode screen powered by BIOS; all they have is a framebuffer device. There a QR code could work really well. No need to have any font data, for instance.
(The screen normally remains white on black. The console can as well be a COM port.)
You can configure it to auto-reboot by putting a timeout value to /proc/sys/kernel/panic.