I was expecting to see 10s of keyboards as you'd see from most in r/MechanicalKeyboards and was disappointed to only find 5. Not an unhealthy relationship at all!
Version 1 used a Teensy++ and Box Pale Blue switches. Version 2 used a Teensy++ and Matias Click switches, and added a bodged-on OLED. This required a completely new PCB design. Version 3 used the same PCB, and some more Matias switches from my parts box, but swapped in a nanoCH32V305 controller using a little interposer adapter board. It was mostly to work the kinks out of the custom firmware for the CH32V305. Version 4 ended up with footprints to use either Alps or MX-footprint switches and either the Teensy or nanoCH32V305. I now have stacks of spare PCBs and plates, just waiting for a better switch than Box White v2.