Listing group members by surname

I have implemented the shortcode for listing group members by ID on a WP page (as per the script on https://www.ads-software.com/support/topic/plugin-user-groups-list-group-members). But i’m wanting to sort the members listed by surname.

How do I do that?
Is someone able to modify the code to make it possible?

add_shortcode('group-list', 'my_group_list_shortcode');
function my_group_list_shortcode( $atts ) {
    // Get the global $wpdb object
    global $wpdb;

    // Extract the parameters and set the default
    extract ( shortcode_atts( array(
        'group' => 'No Group' // No Group is a defined user-group
        ), $atts ) );

    // The taxonomy name will be used to get the objects assigned to that group
    $taxonomy = 'user-group';

    // Use a dBase query to get the ID of the user group
    $userGroupID = $wpdb->get_var(
                    $wpdb->prepare("SELECT term_id
                        FROM {$wpdb->terms} t
                        WHERE t.name = %s", $group));

    // Now grab the object IDs (aka user IDs) associated with the user-group
    $userIDs = get_objects_in_term($userGroupID, $taxonomy);

    // Check if any user IDs were returned; if so, display!
    // If not, notify visitor none were found.
    if ($userIDs) {
        $content = "<div class='group-list'> <ul>";
        foreach( $userIDs as $userID ) {
            $user = get_user_by('id', $userID);
            $content .= "<li>";
            $content .= get_avatar( $user->ID, 70 );
            $content .= "<h3>" . $user->display_name . "</h3>";
            $content .= "<p><a href='". get_author_posts_url( $user->ID ) . "' class='more-info-icon'>More info</a>";
            $content .= "<!-- add more here --></p>";
            $content .= "</li>";
        }
        $content .= "</ul></div>";
    } else {
        $content =
        "<div class='group-list group-list-none'>Returned no results</div>";

    }
    return $content;
}

https://www.ads-software.com/plugins/user-groups/