If I do a lookup() to another list to retrieve a Person field - in this case branch manager, I get a value
How do I get the account name etc to set a people picker field on the form?
So I tried that - and it does work - however for some reason it looks like no value is returned for users who have not signed into the site collection. So I ended up using the SP REST API to load the data
Set "Show field" attribute to "Account" in SharePoint list column settings for the Person field to get account by lookup function.
If You need also Name attribute in SharePoint list, You can create a list workflow to set one field based on the value of the other field when item is created or modified.
Retrieving data ...