Actually I got it right, you just have to change extra parameters to --device=/dev/dri and when you spin up the container, open OBS, settings, streaming, advanced, you will see that there's the hardware encoder available for usage. The problem now is that this container seems abandoned by the dev and the latest one has broken NDI implementation where under sources, NDI doesn't even show up. Sigh, it would be nice if @patrickstigler would come back to this.