It turns out one of the feature limitations of the AMDGPU Linux graphics driver is HDMI 1.4 3D output support with frame packing, top-and-bottom, and side-by-side options for transmitting simultaneous video streams. I wasn't aware of this limitation for the lack of any 3D displays and many Linux enthusiasts/gamers as well, but if you happen to have a compatible HDMI 1.4 3D display, there are pending patches to finally make this a reality...