This is in the realm of ignorant questions. It could well be that the majority of computer devices have none. E.g. the micro controller in my washing machine

Why is it an ignorant question? The nicer ones let you use JTAG etc connections, and debug to console using ITM or RTT. (STM, nRF etc) Others allow debugging via serial.

> Why is it an ignorant question? The nicer ones let you use JTAG etc connections, and debug to console using ITM or RTT. (STM, nRF etc) Others allow debugging via serial.

Because all those systems, even the very nicest, all over the palnet, very really have "JTAG etc connections,"

Those are things you attached to the system. You attach them in a complex error prone process, at the end of it you have a different system.

A lot of (most?) computers do not have consoles.

It is a common error amongst developers (who do not work in embedded systems) to assume there is a screen supporting text of some sort. It is an error

You connect the debug probe to your MCU (pogo pins or w/e is convenient for the form factor), connect it to a PC over USB, and print to a terminal window in Windows, Linux etc. Or a serial-USB bridge if it doesn't support debug probes. If the MCU is so basic it doesn't support UART, bit-bang it with GPIO. Too easy!

> Print debugging is a technique that will never go out of style. It works on any system,

So if you connect up a bunch of wires and everything goes well "too easy" you can get output from some, not all, systems.

What you describe is no what the comment about "print debugging" means, to me.