Does anyone have experience with openpilot? It is an aftermarket kit that in theory could work on the Clarity. I wonder if an Accord or Civic harness would work on the Clarity. https://comma.ai/
If the new product works with the Accord, then there's a chance it will work with the Clarity, too. However, if it would require a significant effort to adapt the product for the Clarity, it's unlikely the company would do that because the Clarity is such a rare car.
The Comma Two isn't supported for the Clarity, but someone who has been working hard on development for the Clarity with the other products (and quite successfully) is getting a Comma Two shipped to them this week and planning on porting it. Should have support soon if there are no major roadblocks.