I built a wireless Corne keyboard from a kit. It uses nice!nano controllers running ZMK. Previously when I used a Kinesis Advantage 2 I replaced its controller board with a KinT which uses a Teensy as its controller. Customizing the keyboard with custom firmware is much nicer than customizing in the OS. But it can be a commitment. Although there are some keyboards that come the reprogramming options out-of-the-box, like the Kinesis Advantage 360, the Moonlander, all of Keyboardio's models.