Ensure ascii on items fallback

src/LanguageInflector.php

@@ -19,6 +19,8 @@ use Drupal\Core\Config\ImmutableConfig;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 
+use function Symfony\Component\String\u;
+
 /**
  * Language inflector service.
  */
@@ -174,7 +176,8 @@ class LanguageInflector {
 
     // Failsafe pluralize if singular and plural are the same.
     if ($plural === $singular) {
-      $plural .= '_' . $this->t('items');
+      $suffix = (string) $this->t('items');
+      $plural .= '_' . u($suffix)->ascii()->lower()->toString();
     }
 
     return $plural;