This Arduino Extender Box Adds a Joystick and Rotary Controls to a Keyboard - Hackster.io
ArtStation - Artist hotkey mechanical keyboard (Arduino)
How I Made: A PCB Mechanical Keyboard — HackSpace magazine
Rcmall 4 Keys Rgb Mechanical Keyboard Module Rainbow Led Max-key Sk6812 Rgb Full Color Led Button For Arduino Building Blocks - Propulsion - AliExpress