Is the Docker container a GPU Emulator

I am trying to make a start experimenting with Riva, and found the rather scary and confusing guide here:

I have a Linux server with ample free RAM/CPU, but do not have a GPU. Actually I have a NVIDIA Jetson Nano but the documentation says that is not supported. It isn’t clear from the guide if the Docker container is a emulator for the GPU or serves some other purpose.

Is buying an expensive GPU the only option open to start playing around with this technology?

Moved to Docker forum.