neither posts, nor manuals can be 100pct relyable without knowing what the exact situation is. so one is always in task of reading and translating those words. I only wrote, what worked for me - i do have cng1, no opencl, that worked exactly as i wrote. te did not say which card he uses, and for opencl i wrote it “should” work - not that it will work as precisly as written. i am able to translate to suse, if its ubuntu… but i like your clear words, thanks 
After reading all manuals and testing, at least i don’t have the impression, that opencl works on amdgpu. It could be related to my hardware - but i rather guess its not compatible with amdgpu (non pro) standalone.
As i am not interested in opencl, as vulkan is fine for me, which works like this, so this is only info * that it might not work even on old chips with amdgpu *:
Downloading this:
https://drivers.amd.com/drivers/linux/amdgpu-pro-21.30-1286092-sle-15.3.tar.xz
and extracting + doing the headless-mode only
>amdgpu-pro-21.30-1286092-sle-15.3 # ./amdgpu-install --opencl=legacy,rocr --headless --no-dkms
(does not matter, if rocr or pal is included - same result)
does install and implements opencl, but devices are not detected:
~> clinfo
Number of platforms 1
Platform Name AMD Accelerated Parallel Processing
Platform Vendor Advanced Micro Devices, Inc.
Platform Version OpenCL 2.0 AMD-APP (3314.0)
Platform Profile FULL_PROFILE
Platform Extensions cl_khr_icd cl_amd_event_callback
Platform Extensions function suffix AMD
Platform Name AMD Accelerated Parallel Processing
Number of devices 0
NULL platform behavior
clGetPlatformInfo(NULL, CL_PLATFORM_NAME, ...) No platform
clGetDeviceIDs(NULL, CL_DEVICE_TYPE_ALL, ...) No platform
clCreateContext(NULL, ...) [default] No platform
clCreateContext(NULL, ...) [other] No platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_DEFAULT) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_CPU) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_GPU) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_ACCELERATOR) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_CUSTOM) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_ALL) No devices found in platform
>~ # lshw -c video | grep driver
configuration: depth=32 driver=amdgpu latency=0 resolution=1280,1024
~ # lspci | grep Radeon
02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Pitcairn PRO [Radeon HD 7850 / R7 265 / R9 270 1024SP]
maybe there is some env missing and it would work, you may know…