With this neat little technique you can identify the user who invoked a flow from a Power App irrespective of the account that actually runs the flow
Flow User
The user’s name, email or GUID can be identified and captured, and it’s as simple as initialising a string variable and setting its value to one of the following
triggerOutputs()[‘headers’][‘x-ms-user-name’]
triggerOutputs()[‘headers’][‘x-ms-user-email’]
triggerOutputs()[‘headers’][‘x-ms-user-id’]
Nice and simple!
A couple of items to bear in mind:
It only works at the top level, ie the flow directly invoked from a Power App. It won’t work for a child flow. In reality that’s not a problem, simply capture the data in the first flow and pass to child flows as a variable
The GUID returned is the user’s GUID in Active Directory, not the GUID for the user’s record in the User table for the current environment, which is different