GPU offload with OpenMP

Hi,
I’m struggling to find informations on how to target GPUs with clang.
My code compiles, it just doesn’t create multiple threads nor omp_is_initial_device() returns a value different than zero.
I tried using Clang 12 downloaded from github (llvm-project/releases) and Visual Studio 2019 Community with LLVM Compiler Toolchain and I’m able to successfully target CPUs but not GPUs.
I tried my compiled code on 2 notebooks and on a desktop pc equipped with a nvidia 1060.
Is there any documentation or can someone give some hints on what one should do to enable the compiled code to spawn threads on the GPU?

Thanks in advance.