FWIW I got it working with rust and opencl, most of it is written by chatgpt as I have no clue about opencl.
GPU usage is only 50-60% and I get 100MH/s.
With hashcat and opencl I could get 12GH/s but I couldn't find a way to use hashcat for this use case.
With hashcat and opencl I could get 12GH/s but I couldn't find a way to use hashcat for this use case.