VDPAU and gpu offload

I am using nvidia 440.31 drivers + an intel integrated graphics with modesetting on a Dell notebook. The discrete GPU is a 1050 Ti Mobile, kernel is 5.3.13 running on Manjaro linux.

I can get the offload to work for rendering, as shown below:

$ __NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia glxinfo |grep 'renderer string' 
OpenGL renderer string: GeForce GTX 1050 Ti with Max-Q Design/PCIe/SSE2

But I still unable to make VDPAU support work as offloading. I’ve tried many different combinations of environment variables with no success:

$ __NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia VDPAU_DRIVER=nvidia vdpauinfo
display: :0   screen: 0
Error creating VDPAU device: 1

I also tried

DRI_PRIME=1

as a longshot but no dice there either.
Is that kind of offloading even possible?

I have same problem on Fedora 33, did you ever found a solution?