To start, an Arduino Uno accepts inputs from a keyboard which handles the incoming serial signals from the keyboard. From there, two Arduino Pro Micros ... available in the project’s repository ...

PD Micro is the first Arduino-compatible board with USB Type-C Power Delivery, which allows your project to make use of voltages from 5-20 V. It’s perfect for projects that would require ...

as described in this SparkFun tutorial (actually for the Arduino Pro Micro). Except, I could not get these to work – the compiler balked at compiling them – and I have no idea what thing I have to add ...

Beyond the Pi the parts list is pretty short, and mainly boils down to the 3D printed enclosure and the components required for the QWERTY board: 43 tactile switches and a SparkFun Pro Micro.