Populate a People control with an email address using a form rule

We would like the ability to set a People control value using a form rule in both the start form and the task form.

The reason we would like this functionality is so that we can populate a People field with a person’s manager. We have the capability to get the manager, but we need to be able to populate a field with that value. We currently have to set a text field to the managers name and another one with the manager’s email, but it would be amazing if we could set a People field with the manager instead.

We have a form where we’d like the submitter to change the approver, which defaults to the manager. In the screenshot provide, we’d like to set the approver field to the manager, and allow the submitter to change it.