Try implementing a normalizer for integerdata

jsonld.services.yml

@@ -40,3 +40,8 @@ services:
   jsonld.normalizer_utils:
     class: Drupal\jsonld\Utils\JsonldNormalizerUtils
     arguments: ['@config.factory', '@language_manager', '@router.route_provider']
+  jsonld.normalizer.integer_data:
+    class: Drupal\jsonld\Normalizer\IntegerDataNormalizer
+    tags:
+      - { name: normalizer, priority: 5 }
+

src/Normalizer/IntegerDataNormalizer.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Drupal\jsonld\Normalizer;
+
+use Drupal\Core\Field\FieldItemInterface;
+use Drupal\Core\TypedData\Type\IntegerInterface;
+use Drupal\serialization\Normalizer\NormalizerBase;
+use Drupal\serialization\Normalizer\SerializedColumnNormalizerTrait;
+
+/**
+ * Converts integer data objects to their casted values.
+ */
+class IntegerDataNormalizer extends NormalizerBase {
+
+  use SerializedColumnNormalizerTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function normalize($object, $format = NULL, array $context = []): array|string|int|float|bool|\ArrayObject|NULL {
+    // Add cacheability if applicable.
+    $this->addCacheableDependency($context, $object);
+
+    $parent = $object->getParent();
+    if ($parent instanceof FieldItemInterface && $object->getValue()) {
+      $serialized_property_names = $this->getCustomSerializedPropertyNames($parent);
+      if (in_array($object->getName(), $serialized_property_names, TRUE)) {
+        return unserialize($object->getValue());
+      }
+    }
+
+    // Typed data casts NULL objects to their empty variants, so for example
+    // the empty string ('') for string type data, or 0 for integer typed data.
+    // In a better world with typed data implementing algebraic data types,
+    // getCastedValue would return NULL, but as typed data is not aware of real
+    // optional values on the primitive level, we implement our own optional
+    // value normalization here.
+    return $object->getValue() === NULL ? NULL : $object->getCastedValue();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getSupportedTypes(?string $format): array {
+    return [
+      IntegerInterface::class => TRUE,
+    ];
+  }
+
+}