The User field selects one or several users of the site, with their avatar shown in the search results.

Configuration
Go to Modern Fields > Fields groups and add the User field. Its settings are in the inspector:
| Effect | |
|---|---|
| Searchable roles | Only offer the users having these roles, custom roles included. |
| Allow several users | Lets the user select more than one user. |
Display the users
The field stores user IDs. Read them with get_field():