What is QMK?
QMK (Quantum Mechanical Keyboard Firmware) is custom firmware that supports a variety of keyboards, mice, and MIDI devices. It supports a variety of features such as remapping keys and RGB control at a hardware level among many other things. You can learn more about QMK here: https://docs.qmk.fm/
Why Does it Matter For SignalRGB?
The reason that QMK matters to SignalRGB is that QMK allows us to support DIY keyboards and boards with firmware that otherwise would not work with Signal. This allows us to support a much wider userbase of devices than would be possible without QMK.
What Are the Drawbacks of QMK?
The main drawbacks of flashing and using QMK are the chance to brick your keyboard, and the fact that the keyboard will no longer work with its original software if it had any.