Leave the console visible on an attached monitor. I don’t recall if Debian out-of-box has Ctrl-Alt-F1 disabled, but if not, that’ll put you on the first console. If the kernel panics, it’ll display something there.

If you can’t do that — no spare monitor — you can set up a serial port console to another machine. I don’t know off the top of my head how to have the kernel emit errors there by default if it’s not the default, but I’m quite sure that it’s possible; I’ve debugged machines with kernel stack traces on serial port consoles. Sending a BREAK was equivalent to Magic Sysrq, as I recall.