I have used "Microsoft Visual Studio Community 2019" to build a UWP app that I want to distribute through the Microsoft Store. The app builds without error and works as intended, I have associated the app with a submission in the Partner Center, and the "Select and configure apps" step succeeds. I have been following the instructions here and read about certificates here.
When the "Validating app" process starts it fails almost immediately with an "App not digitally signed" error. When I look at the certificate instructions to me it reads that (1) I can only generate a test certificate and (2) because I am publishing to the Store I don't need a certificate because the Store will handle it and (3) I can't see anywhere how to associate a certificate with an app in Visual Studio.

My broad question is how to submit an app from Visual Studio to the Microsoft Store using VS Community Edition.
My specific question is how do successfully run the "Validate app" step, where do I get a proper production grade certificate (if I need one), and how do I get my App into the Store (I believe I need Visual Studio to create a .appxupload but am not clear).