Row Level Security - External User

Hi there

You would first need to add the external user as part of your AAD, and then assign them access to your dataset, by going into the dataset settings and then clicking on Security.

Here are more details on how to do this. Scroll down to the section, which will explain how to achieve this.

https://docs.microsoft.com/en-us/power-bi/whitepaper-azure-b2b-power-bi#case-study-building-a-bi-portal-using-power-bi--azure-ad-b2b--step-by-step-instructions