The Map widget of Experience Builder currently seems to lack functionality to turn on a dynamic graticule (lat/long) and/or measured grid (easting/northing).
The Functionality Matrix for Web AppBuilder and Experi... - Esri Community mentions in Functionality Matrix for ExB and WAB _March 2022.docx that the addition of "Grid Overlay" functionality has a status of TBD. I am assuming that this is the Graticule and Measured Grid functionality that I am looking for.
It also mentions that "Gridded Reference Graphic" functionality is Planned with No timeline (as yet). I am assuming that this is Reference Grid functionality, which is related to but not the Graticule and Measured Grid functionality that is the subject of this Idea.