On Android, you cannot use the MediaTexture asset directly, unfortunately. You have to create a Material from it and use that instead. Android is a bit special right now in that it uses the new external texture sampler feature for maximum performance. Unfortunately, this means that media textures no longer behave like normal textures.
I’m not sure if there will be a fix for this. We will likely just add a warning in the Editor to inform users about this Android specific behavior.