Issue #3269454: The deprecated alter hook hook_field_widget_form_alter() is implemented in these functions: entity_embed_field_widget_form_alter

entity_embed.module

@@ -286,21 +286,15 @@ function entity_embed_filter_format_edit_form_validate($form, FormStateInterface
 }
 
 /**
- * Implements hook_field_widget_form_alter().
+ * Implements hook_field_widget_single_element_form_alter().
  */
-function entity_embed_field_widget_form_alter(&$element, FormStateInterface $form_state, $context) {
+function entity_embed_field_widget_single_element_form_alter(&$element, FormStateInterface $form_state, $context) {
   // Add a `data-entity_embed-host-entity-langcode` attribute so that
   // entity_embed's JavaScript can pass the host entity's language to
   // EntityEmbedDialog, allowing it to present entities in the same language.
-  if (!empty($element['#type']) && $element['#type'] == 'text_format') {
-    if (!empty($context['items']) && $context['items'] instanceof FieldItemListInterface) {
-      $element['#attributes']['data-entity_embed-host-entity-langcode'] = $context['items']->getLangcode();
-    }
-    else {
-      $entity = $form_state->getFormObject()->getEntity();
-      if ($entity instanceof ContentEntityInterface) {
-        $element['#attributes']['data-entity_embed-host-entity-langcode'] = $entity->language()->getId();
-      }
-    }
+  if (isset($element['#type']) && $element['#type'] === 'text_format') {
+    /** @var FieldItemListInterface $items */
+    $items = $context['items'];
+    $element['#attributes']['data-entity_embed-host-entity-langcode'] = $items->getEntity()->language()->getId();
   }
 }