[ajsnigrutin]

As an non-amateur EE, i fully agree with this. If you can draw a basic circuit for 9 keys on paper, you can draw a full-keyboard one in many of the easy cheap PCB platforms, most of which offer a web interface (no installation of any weird software), rendered 3d views and a very cheap production price.

If you really want to do it without a chinese PCB manufacturer, you can do it on a perf board ( https://en.wikipedia.org/wiki/Perfboard ). If you have more GPIOs than keys (eg when building a very cheap steam deck with 9/12 keys), you don't even need any kind of "matrix" multiplexing, and you can just connect the keys to individual gpio pins. If you take a better microcontroller than a teensy, you also get bluetooth (and wifi) capabilities, like with eg. esp32 (~$5 on aliexpress).

But either way, doing fun electronics, be it on a pcb or when soldering "in the air" is a lot better waste of money and time than many other things most people do.