only in patch2:
unchanged:
--- a/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
@@ -8,6 +8,7 @@
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Entity\FieldableEntityInterface;
 use Drupal\Core\Field\FieldTypePluginManagerInterface;
+use Drupal\Core\Session\AccountSwitcherInterface;
 use Drupal\Core\TypedData\TranslatableInterface;
 use Drupal\Core\TypedData\TypedDataInterface;
 use Drupal\migrate\Audit\HighestIdInterface;
@@ -17,6 +18,7 @@
 use Drupal\migrate\MigrateException;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
 use Drupal\migrate\Row;
+use Drupal\user\EntityOwnerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -102,6 +104,13 @@ class EntityContentBase extends Entity implements HighestIdInterface, MigrateVal
    */
   protected $fieldTypeManager;
 
+  /**
+   * The account switcher service.
+   *
+   * @var \Drupal\Core\Session\AccountSwitcherInterface
+   */
+  protected $accountSwitcher;
+
   /**
    * Constructs a content entity.
    *
@@ -133,7 +142,7 @@ public function __construct(array $configuration, $plugin_id, $plugin_definition
    */
   public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
     $entity_type = static::getEntityTypeId($plugin_id);
-    return new static(
+    $instance = new static(
       $configuration,
       $plugin_id,
       $plugin_definition,
@@ -143,6 +152,8 @@ public static function create(ContainerInterface $container, array $configuratio
       $container->get('entity_field.manager'),
       $container->get('plugin.manager.field.field_type')
     );
+    $instance->accountSwitcher = $container->get('account_switcher');
+    return $instance;
   }
 
   /**
@@ -184,8 +195,18 @@ public function isEntityValidationRequired(FieldableEntityInterface $entity) {
    * {@inheritdoc}
    */
   public function validateEntity(FieldableEntityInterface $entity) {
+    // Entity validation can require the user that owns the entity. Switch to
+    // use that user during validation.
+    if (($entity instanceof EntityOwnerInterface) && $user = $entity->getOwner()) {
+      $this->getAccountSwitcher()->switchTo($user);
+    }
+
     $violations = $entity->validate();
 
+    if (($entity instanceof EntityOwnerInterface) && $user = $entity->getOwner()) {
+      $this->getAccountSwitcher()->switchBack();
+    }
+
     if (count($violations) > 0) {
       throw new EntityValidationException($violations);
     }
@@ -375,4 +396,17 @@ public function getHighestId() {
     return (int) current($values);
   }
 
+  /**
+   * Get the account switcher service.
+   *
+   * @return \Drupal\Core\Session\AccountSwitcherInterface
+   *   The account switcher service.
+   */
+  protected function getAccountSwitcher(): AccountSwitcherInterface {
+    if (!isset($this->accountSwitcher)) {
+      $this->accountSwitcher = \Drupal::service('account_switcher');
+    }
+    return $this->accountSwitcher;
+  }
+
 }