Hi, I think these link below might help you.
https://amdgpu-install.readthedocs.io/en/latest/install-script.html
All though, the Open Source AMD Radeon Ubuntu Driver should be already on your system by default. They're integrated into Mesa and the Linux kernel. So further you need to run some Scripts in order to start using Radeon devices.
Try using the following parameters:
amdgpu-install --usecase=graphics,opencl --vulkan=amdvlk --opencl=legacy