Just to close this loop in this thread. I created a second thread because I was a new user: MS Edge backend fails in Notebook (other than first page)
@DietmarSchwertberger suggested on demand web view creation, which resolves the issue.
I can only speculate about the minimum requirements to get Edge to work in the Notebook. But I could get the page of my choice to work at app launch if the page was selected before web view creation and remained selected though the rest of the app launch. The issue appears not to be related to time, but rather what resources are available to each Notebook page (must be different for a selected page, also before or after app launch completion).