Power Bi doesn’t give you a way to get a list of users who you have granted access to an app. This is different to the list of users who have access to a workspace, which you can get using the API.

Go to Power Bi and choose to update app, then go to the the permissions tab and you can see that the list just shows names, and you cannot export.

app-permissions

Open Chrome F12 dev tools, and inspect a users name and you can see that there is a title attribute that contains the User Principal Name which we are interested in.

f12

In the console at the bottom, paste this command to return a semi-colon delimited list of UPNs:

$$("span[class=displayName]").forEach(user => { console.log(user.title + ";") })

console