There is a post from 2016 about not being able to "Share" a PowerApp with B2B guest users. This is now available in Power BI:
https://powerbi.microsoft.com/en-us/blog/power-bi-expands-access-to-intelligence-for-external-guest-users/
so I find it hard to believe that it's not available in Power Apps yet. However, when I try to "Share" with a B2B Guest user (they have a Office 365 E3 account and Power Apps license in their own tenant so it's not a license issue) I get an error "[Guest user email address] is not in your organization's directory", which makes no sense because I can see it in my list of users in my directory.
Do I need to give the Guest user some special access in my Azure Active Directory in order for share a Power App with them? Has anybody been able to successfully share with B2B Guest users?
If not, this really restricts the usefulness of Power Apps!
Thanks,
Kathryn