Many people already have run X in a container with no trouble. They often just vnc it out. The hard part is not running X, but running X and having it display

Many people already have run X in a container with no trouble. They often just vnc it out. The hard part is not running X, but running X and having it display to your hardware. This is a massive distinction. You need to passthrough your graphics device so that X can write to its framebuffer and all that bizzazz, and that's the question you really should be asking. "How do I pass my graphics device / display device into a container".