In case anyone wants to know, the keyboard is a Kyria split keyboard from splitkb.com. Apart from the PCB kit I had in it two Elite-C controllers, OLED displays, two rotary encoders with industrial knobs and acrylic plates for case. Further complemented with switches and keycaps.
At minimum you need the PCB kit, two controllers, a TRRS cable, switches and keycaps.
The page I linked explains this, so be sure to read up.
I have enjoyed the project build so much that I kinda rolled into toying around with other controller boards, I’ve got now a couple of Teensy 4.1 boards and a bunch of WeAct blackpills. This is my first foray into this kinda stuff, but hugely interesting.