i have just set up a gateway to our sharepoint 2013 on premise and have created a sharepoint powerapp for a simple list. I have two columns for people. The first one for people only and the second one for people and groups.
The behavior of the people picker is as follows: 1. ViewMode Empty i.e. absolutely no people, or groups visible 2.1 EditMode PeopleOnly: search by name, dropdown appears briefly and disappears immediately, without the possibility of selection 2.1 EditMode PeopleAndGroups: search by name, dropdown shows up, person can be selected, but is not displayed after selection