Mohit Aghera
--- a/core/modules/jsonapi/src/Controller/EntityResource.php
+++ b/core/modules/jsonapi/src/Controller/EntityResource.php
    $this->serializer = $serializer;
    $this->time = $time;
    $this->user = $user;
+    if ($language_manager === NULL) {
+      @trigger_error(__NAMESPACE__ . '\EntityResource::__construct() without the language_manager service is deprecated in drupal:10.2.3 The language_manager dependency was added in drupal:10.2.3 and will be required before drupal:11.0.0. See https://www.drupal.org/node/3357049', E_USER_DEPRECATED);
--- a/core/modules/jsonapi/src/Controller/EntityResource.php
+++ b/core/modules/jsonapi/src/Controller/EntityResource.php
   */
  protected $user;

+  /**
+   * The language manager.
+   *
+   * @var \Drupal\Core\Language\LanguageManagerInterface
+   */
+  protected $languageManager;
-  protected $languageManager;
+  protected LanguageManagerInterface  $languageManager;
--- a/core/modules/jsonapi/tests/src/Kernel/Controller/EntityResourceTest.php
+++ b/core/modules/jsonapi/tests/src/Kernel/Controller/EntityResourceTest.php
    $this->assertEquals(['node_list'], $response->getCacheableMetadata()->getCacheTags());
  }

+  /**
+   * Test the language_manager argument deprecation.
+   *
+   * @group legacy
+   */
+  public function testEntityResourceNewParameterDeprecation(): void {
+    $this->expectDeprecation(EntityResource::class . '::__construct() without the language_manager service is deprecated in drupal:10.2.3 The language_manager dependency was added in drupal:10.2.3 and will be required before drupal:11.0.0. See https://www.drupal.org/node/3357049');