first you need the alpha img file which is here
then you need to update the driver manually:
#cd /hive-driver-pack
download the latest driver:
#wget https://drivers.amd.com/drivers/linux/amdgpu-pro-20.30-1109583-ubuntu-18.04.tar.xz
decompress it:
#tar -Jxvf amdgpu-pro-20.30-1109583-ubuntu-18.04.tar.xz
enter the directory:
#cd amdgpu-pro-20.30-1109583-ubuntu-18.04
uninstall current driver:
#amdgpu-uninstall
install with the new:
#./amdgpu-pro-install --opencl=pal,legacy