Brute Force Matcher with OCL won't run on GPU

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The ocl implementation of the brute force descriptor matcher won't run on GPU while other algorithms like Surf do. I've tried on ubuntu 18.04 with AMDGPU (amd RX580), ubuntu 19.04 with mesa on same computer and 19.04 with mesa on laptop with nvidia gpu.

opencv_version --opencl https://pastebin.com/1JD1J1Ax

getBuildInformation() https://pastebin.com/hEhq0hKK

I've made a minimum project to test this. Running this while monitoring CPU and GPU activity I can check my cpu cores get near 90% utilization while gpu remains idle. (Might need a bigger test file to notice if your cpu is too fast). https://drive.google.com/file/d/1hoB7...

Any idea on what could be going wrong???

Thx in advance.