I decided to contribute my GPU on my Ubuntu-based system to the Folding@Home effort for COVID-19. I kept getting this error message for my NVIDIA GeForce GTX 1050 TI when I tried:
ERROR:WU00:FS00:Failed to start core: OpenCL device matching slot 0 not found, make sure the OpenCL driver is installed or try setting 'opencl-index' manually
I had the nvidia opencl packages installed but apparently missed something. I finally found on the folding at home forum what I was missing – ocl-icd-opencl-dev
sudo apt install ocl-icd-opencl-dev
After running the above command and restarting the FAHClient service, the GPU started folding. For science!
EDIT 5/6/2020: After a re-install I had the issue where the GPU wouldn’t show up at all. It addition to
ocl-icd-opencl-dev, it looks like you also need
sudo apt install ocl-icd-opencl-dev nvidia-cuda-dev