Nice shield, for anyone wondering. Here is the pinout I’ve sussed out for the transmitter shield.
L1 = Pin(0)
L2 = Pin(1)
L3 = Pin(2)
R1 = Pin(3)
R2 = Pin(4)
R3 = Pin(5)
Still working on figuring out the digital switches, maybe later today. Unfortunately documentation is still painfully lacking on this ecosystem.