Update config.yml

_config/config.yml

@@ -10,6 +10,7 @@ SilverStripe\Core\Injector\Injector:
     class: Symbiote\Addressable\MapboxGeocodeService
 
 SilverStripe\SiteConfig\SiteConfig:
+  map_type: "google-maps"
   extensions:
     - A2nt\SilverStripeMapboxField\SiteConfigExtension
 

src/SiteConfigExtension.php

@@ -4,6 +4,7 @@
 namespace A2nt\SilverStripeMapboxField;
 
 use SilverStripe\Core\Extension;
+use SilverStripe\Core\Config\Config;
 
 class SiteConfigExtension extends Extension
 {
@@ -11,6 +12,26 @@ class SiteConfigExtension extends Extension
     {
         return MapboxField::getAccessToken();
     }
+    
+    public function MapAPIKeyFrontend(): string
+    {
+        $type = $this->owner->config()->get('map_type');
+
+        switch ($type) {
+            case 'mapbox':
+                $key = MapboxField::getAccessToken();
+                break;
+            case 'google-maps':
+                $cfg = Config::inst()->get(GoogleMapField::class, 'default_options');
+                $key = isset($cfg['api_key']) ? $cfg['api_key'] : '';
+                break;
+            default:
+                $key = '';
+                break;
+        }
+
+        return $key;
+    }
 
     public function MapStyle()
     {