Working example of ARBackgroundRendererAsset ?

My goal is simple: to get AR Camera Background to render the camera image on the screen of my iOS device while using LWRP. Right now, it renders black. If I remove LWRP, it renders correctly.

From official threads with missing Github projects to minimally helpful documentation, getting this up and running is proving to be a long and draining process of blindfolded experimentation. I am hoping that Unity (or the community) has a working example I can try to learn from.

For example, one thing that's confusing me is the use of background materials. There are 3 different references to different and/or same materials:

• ARCameraBackground.CustomMaterial
• ARBackgroundRendererAsset.CreateCustomMaterial
• ARFoundationBackgroundRenderer.backgroundMaterial

The relationship between these objects -- when only one material will end up being used -- is quite a mystery.

I am using Unity 2019.2.5f1 with AR Foundation 2.1.1 and Lightweight RP 6.9.1.

Thanks in advance for any assistance you can offer.