On one of my systems (Manjaro/Arch) I have just made a full system reinstall. OpenCL appears to have gone in correctly but is not seen by DT.
[opencl_init] opencl library ‘libOpenCL’ found on your system and loaded
[opencl_init] no platform (0) detected: Unknown OpenCL error
[opencl_init] FINALLY: opencl is NOT AVAILABLE and NOT ENABLED.
In the DT preferences/processing the driver is shown as being in place.