Securely share report with non-pro users

hi, adonovan 

For normal, if you want to share a private report to others, you and others both need the Pro license.
If you have purchased Premium and add your content to Premium, then when you share the content, the receiver could be free user.
https://docs.microsoft.com/en-us/power-bi/service-free-vs-pro
https://docs.microsoft.com/en-us/power-bi/service-premium

Another way, you could publish report to web, then anyone could access it.

But When you use Publish to web, the report or visual you publish can be viewed by anyone on the Internet. There is no authentication used when viewing these reports. Only use Publish to web with reports and data that the anyone on the Internet (unauthenticated members of the public) should be able to see. This includes detail level data that is aggregated in your reports. Before publishing this report, ensure you have the right to share the data and visualizations publicly. Do not publish confidential or proprietary information. If in doubt, check your organization's policies before publishing.

https://docs.microsoft.com/en-us/power-bi/service-publish-to-web

Best Regards,
Lin