Based on this pinout the audio cable for Digirig would look like this:
RJ-45 pin 4 (Ground) → 3.5mm TRRS sleeve (GND)
RJ-45 pin 5 (Mic) → 3.5mm TRRS ring 1 (RIG_AFIN)
RJ-45 pin 6 (PTT) → 3.5mm TRRS ring 2 (RIG_PTT)
Assuming there is no RX audio on the mic connector we’ll need a separate jack for headphones jack:
3.5mm TRS tip (SPK) → 3.5mm TRRS tip (RIG_AFOUT)
Depending on the source the pins on RJ-45 are numbered in different directions. It would be helpful to have some confirmation. You can ring pins to the chassis and whichever have continuity are going to be pin 4.
The above layout is almost FT-2500 reversed pinout. If the mic connector has the RX audio next to PTT (pin 7 or pin 2 depending on direction), then it is a match. 5V and connections for buttons do line up.