I decided to add an ESP32 to take input from the keypad, 5 buttons and the 2 rotary knobs. It would also control the single color OLED in the top of the case as well as a planned external color LCD (currently not installed).
The idea is to allow the control of the SDR via the knobs and quickly start a program or enter a frequency either via keypad or rotary knob. Communication with the Pi is not yet defined but maybe via serial port or SPI.
To connect everything up neatly created the following PCB.
The PCB also connected the 5 buttons that control the display (this is just to clean things up). The USB port is not used.
Very basic circuit with nothing special about it.