I have a question regarding permissions on PowerApps. I know external users from the current tenant are not able to use any PowerApps app. Here the official documentation and here from PowerApps Q&A.
But, is there a way to have trusted accounts or accounts from trusted domains and grant access to PowerApps apps? If not, is it in the current PowerApps roadmap and the roll out date for it?
Very good research, and those are great links.
Yes, currently PowerApps is limited to single Organization (tenant), nothing can be done to open it up/share across any other trusted tenants.
PowerApps portals is the one you are looking for, which can be established to external domain users (B2C & B2B).
PowerApps portals in private preview now, it will be available for Public preview from Jul '19 maybe. This was announced on Microsoft Business Applications Summit on June 10th 2019.
Introducing PowerApps Portals: powerful low-code websites for external users