Hi @Letsinger, Dan,
Great to know that and thanks for sharing the update here.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.". and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[Does the SharePoint Online automatic news digest email get sent to guest users?]
Issue Symptom:
Does the SharePoint Online automatic news digest emails get sent to guest users?
Current status:
SharePoint Online automatic news digest emails do not get sent to guest users.
You could click the "Accept Answer" button for this summary to close this thread. By doing so, it will benefit all community members who are having this similar issue. Your contribution is highly appreciated!