A handwired QMK keyboard would work fine: https://docs.qmk.fm/#/hand_wire https://docs.qmk.fm/#/hand_wire If you have only one or two switches, you can use the

A handwired QMK keyboard would work fine: https://docs.qmk.fm/#/hand_wire https://docs.qmk.fm/#/hand_wire If you have only one or two switches, you can use the DIRECT_PINS configuration to directly put one switch per input pin rather than the more conventional switch matrix approach. You can use the XD002 code as a starting point (https://github.com/qmk/qmk_firmware/tree/master/keyboards/xd002 https://github.com/qmk/qmk_firmware/tree/master/keyboards/xd..., https://github.com/qmk/qmk_firmware/blob/master/keyboards/xd002/config.h#L36 https://github.com/qmk/qmk_firmware/blob/master/keyboards/xd...). It uses a DigiSpark rather than the more common Arduino Pro Micro. The DigiSpark is a bit fiddly and has very little program memory, but it is very cheap and simple.