Hello All,
The solutions presented did not address the issue sufficiently, but I will add what I have discovered in the hopes that it will aid someone else who finds themselves in the same/similar situation in the future.
In order to test an offering, it is absolutely necessary to create an account which is external to your organization. Adding guest users to your tenant is insufficient, as is testing with internal users. The account must be truly external to fully test the end-user experience and to find issues with your offering.
Microsoft seems averse to allowing the creation of user accounts for this purpose (note the elimination of the ability to use "personal" accounts for this purpose); there seems to be an effort to eliminate the methods for setting up these accounts as they are discovered, so there is little point in adding links here to show how to do it. The tester will need to use their favorite search engine to find the latest method as things evolve.
Once I created a truly external user to my organization, I have found it possible to set that account up with a trial version of PowerBI to download/test my sample application. Further verification was provided from an acquaintance with student account access.
Thank you for your time and consideration,
Ix Jr.