You will find a download link to a postprocessor specifically for V1 machines in this topic. While generic GRBL postprocessors will work with the Jackpot board, there are specific issues associated with V1 machine. In particular, the Z axes have different federate limits than the X and Y axes, and Don Gamble’s postprocessor makes some provisions for this difference.
Don did mention at one point that he did not personally test the postprocessor wrt GRBL, but I believe Jackpot users have successfully his postprocessor.