And old question and not sure if the information is still relevant or answered elsewhere.

The URIs you will need for this information will be read scopes to:

"https://graph.microsoft.com/v1.0/devices/" and "https://graph.microsoft.com/v1.0/users/"

The information is located in the "physicalIDs" property retrieved from the "Devices" uri, which must be parsed and used to retrieve the user with the "Users" uri

The phsycialIDs is an array containing objects with "[ID]:Value" format as a strings.

The one you need here is the "[USER-GID]" property. This can be split by the ":" delimiter.

The array elements are not in a standardized order, so you will need to find the associated [USER-GID] element manually.

It will most likely be in the format: [USER-GID]:{guid}:{device attributer number}

You can then use the GID GUID retrieved here to resolve the associated identity with the Users URI.