ARKit / SpriteKit - set pixelBufferAttributes to SKVideoNode or make transparent pixels in video (chroma-key effect) another way

The solution is quite simple! All that needs to be done is to add the video as a child of a SKEffectNode and apply the filter to the SKEffectNode instead of the video itself (the AVVideoComposition is not necessary). Here is the code I used:

func view(_ view: ARSKView, nodeFor anchor: ARAnchor) -> SKNode? {
    // Create and configure a node for the anchor added to the view's session.
    let bialikVideoNode = videoNodeWith(resourceName: "Tsina_05", ofType: "mp4")
    bialikVideoNode.size = CGSize(width: kDizengofVideoWidth, height: kDizengofVideoHeight)
    bialikVideoNode.anchorPoint = CGPoint(x: 0.5, y: 0.0)

    // Make the video background transparent using an SKEffectNode, since chroma-key doesn't work on video
    let effectNode = SKEffectNode()
    effectNode.addChild(bialikVideoNode)
    effectNode.filter = colorCubeFilterForChromaKey(hueAngle: 120)

    return effectNode
}

And here is the result as needed: