You can use the User function (https://powerapps.microsoft.com/en-us/tutorials/function-user/) or the office 365 connector (https://powerapps.microsoft.com/en-us/tutorials/connection-office365-outlook/) to find out who the user is and navigate to a particular screen based on the user.
For example,
If(
User().Email = "user@domain.com",
Navigate(screen1),
Navigate(screen2)
)
If you have any questions or feedback, please let me know. Have a great day! 😊
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