raspi-config is just a shell script with minimal dependencies. Grab a copy from here:
For most things including this it should work fine as Raspbian is in fact nearly identical to Debian. There may be a few thing that require the userland tools but this is not one of them.
All it appears to to do is add
/boot/config.txt, and, if you want the serial line console disabled (you probably do if you want to do anything other than login or observe system messages over UART), it removes
/boot/cmdline.txt. The best bet is to change that to
console=tty1, which will put system messages on a virtual console (the one you see on the screen if you boot without a GUI).
config.txt documentation regarding the UART is here: https://github.com/raspberrypi/documentation/blob/master/configuration/uart.md