AFAIK the keyboard in question only uses USB for charging. It can't send keys over the wire.
That said, before getting the MX keys I bought a Dell 7440 keyboard on ebay for $20, fastened it on top of a 6mm clear acrylic plate with M3 screws, along with a Teensy chip running kbd firmware:
https://www.instructables.com/How-to-Make-a-USB-Laptop-Keybo...