Can't open camera by index on LXC container

This part is related to GL support in the container. You would first need to be able to run a simpler application, such as glxgears or glxinfo.

Having said that, the rest of the errors are with the camera device itself.
I have not tested these and I do not know what how best to resolve them.
Specifically, I am not sure which device files have to be made available in the container.
As a hint during research, you would try to web search for terms like use webcam in docker.
In addition, I would also try to use a plain UVC application, such as guvcview or uvccapture.