Lightning Web Component embedded in Visualforce Page via Aura Component and App not displaying

With Summer 19 release, now its possible to use LWC in visualforce as lightning out.

https://www.paul-force.com/2019/04/24/use-lightning-web-components-in-visualforce-pages/ https://releasenotes.docs.salesforce.com/en-us/summer19/release-notes/rn_lwc_vf.htm

It is not supported behavior. While some standard components are actually LWC, they are given an exception (otherwise Lightning Out would be useless). For now, custom LWC are not supported in an unsupported environment, no matter how you dress it up.