up:: PowerApps
In order to change Person or Group in Power Apps, you should use record data in DefaultSelectedItems (JSON syntax):
{
Claims: "i:0#.f|membership|"&person.Email,
DisplayName: person.DisplayName
}
{
'Created by'.Claims = "i:0#.f|membership|"&User().Email
}
Default values for complex SharePoint types
How to update Single or Multi person field in SharePoint from Power Apps Canvas apps
Solved: Set People Picker with current user and another list - Power Platform Community