PowerBI . embedded on Sharepoint with external users

Hi OnDaRoXx 

To give users free secure access to Reports you need a Premium Capacity licence. This is good if you have many people (>400) that need to view Reports. If you only have a few users that need to view Reports securely it will be cheaper to buy them a Pro licence each.

The Premium Per User (PPU) licence is for people who want some of the benefits of Premium Capacity (Larger Datasets, faster Refreshes, Paginated Reports etc.) at a lower entry cost. But be aware here that one PPU licence is not much use, as everyone needs a PPU licence to view content on a PPU workspace.

See : Power BI service features by license type - Power BI | Microsoft Docs

The other alternative is to use "Publish to web" which places the Report on a publicly accessible web store. Anyone can view this Report without a licence, but it is not secure (anyone on the internet could find it) so it should not be used for proprietory information. see: Publish to web from Power BI - Power BI | Microsoft Docs

Hope this helps

Stuart