I can confirm that the Digirig mobile does work with the Kenwood TRC-70 HF Transceiver for audio, through the TRC-70’s mic port (the radio does not have an accessory port).
I built a custom cable to interface them, but it looks like the following cable sold in the Digirig store should work (follow that cable’s schematic if you want to build your own):
Note: as the radio appears to not have a VOX option, ptt via RTS capability will be necessary.
Picture of the radio with Digirig mobile:
Hope this will help anyone else who might have this radio.