Typed data layout_section can't be normalized if it stores object

My reproduced steps:

1. Install drupal8.7.x
2. Install jsonapi2.x-dev, layout_builder
3. Visit /admin/structure/types/manage/article/display and enable
1. Use Layout Builder
2. Allow each content item to have its layout customized.
4. Add an article and set this article's layout

Ouput:

"layout_builder__layout": [
    null,
    null
]

Similar issue with TypedData 'Any' can't be normalized to array if it stores an object
When enable "Allow each content item to have its layout customized" on article
Layout builder add a bundle field "layout_builder__layout" to article.

  protected function addSectionField($entity_type_id, $bundle, $field_name) {
    $field = FieldConfig::loadByName($entity_type_id, $bundle, $field_name);
    if (!$field) {
      $field_storage = FieldStorageConfig::loadByName($entity_type_id, $field_name);
      if (!$field_storage) {
        $field_storage = FieldStorageConfig::create([
          'entity_type' => $entity_type_id,
          'field_name' => $field_name,
          'type' => 'layout_section',
          'locked' => TRUE,
        ]);
        $field_storage->save();
      }

      $field = FieldConfig::create([
        'field_storage' => $field_storage,
        'bundle' => $bundle,
        'label' => t('Layout'),
      ]);
      $field->save();
    }
  }

The layout_section field type definition here: \Drupal\layout_builder\Plugin\Field\FieldType\LayoutSectionItem

class LayoutSectionItem extends FieldItemBase {

  /**
   * {@inheritdoc}
   */
  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
    $properties['section'] = DataDefinition::create('layout_section')
      ->setLabel(new TranslatableMarkup('Layout Section'))
      ->setRequired(FALSE);

    return $properties;
  }

We can see it use layout_section typed data \Drupal\layout_builder\Plugin\DataType\SectionData
Field layout_builder__layout store object value, see below image:

But this typed data "layout_section" can't be normalized if it stores an object.

After add some code like anyNormalizer to TypedDataNormalizer
The jsonapi return :

"layout_builder__layout": [
        [
          {
            "layout_id": "layout_onecol",
            "layout_settings": [],
            "components": {
              "fa860f85-753a-4206-be70-03e0550891d6": {
                "uuid": "fa860f85-753a-4206-be70-03e0550891d6",
                "region": "content",
                "configuration": {
                  "id": "field_block:node:article:changed",
                  "label": "Changed",
                  "provider": "layout_builder",
                  "label_display": "visible",
                  "formatter": {
                    "label": "above",
                    "type": "timestamp",
                    "settings": {
                      "date_format": "medium",
                      "custom_date_format": "",
                      "timezone": ""
                    },
                    "third_party_settings": []
                  },
                  "context_mapping": {
                    "entity": "layout_builder.entity"
                  }
                },
                "additional": [],
                "weight": 1
              },
              "5df8fddf-25e5-4001-9bd0-7cf20897fffe": {
                "uuid": "5df8fddf-25e5-4001-9bd0-7cf20897fffe",
                "region": "content",
                "configuration": {
                  "label_display": "0",
                  "context_mapping": {
                    "entity": "layout_builder.entity"
                  },
                  "id": "field_block:node:article:body",
                  "formatter": {
                    "type": "text_default",
                    "settings": [],
                    "third_party_settings": [],
                    "label": "hidden"
                  }
                },
                "additional": [],
                "weight": 0
              },
              "c0efb163-54e5-47d3-b815-be68a74a80a2": {
                "uuid": "c0efb163-54e5-47d3-b815-be68a74a80a2",
                "region": "content",
                "configuration": {
                  "label_display": "0",
                  "context_mapping": {
                    "entity": "layout_builder.entity"
                  },
                  "id": "field_block:node:article:field_tags",
                  "formatter": {
                    "type": "entity_reference_label",
                    "label": "above",
                    "settings": {
                      "link": true
                    },
                    "third_party_settings": []
                  }
                },
                "additional": [],
                "weight": 2
              }
            }
          }
        ],
        [
          {
            "layout_id": "layout_onecol",
            "layout_settings": [],
            "components": {
              "0dd4b4e5-175d-4c66-b0c6-381f097c43e9": {
                "uuid": "0dd4b4e5-175d-4c66-b0c6-381f097c43e9",
                "region": "content",
                "configuration": {
                  "label_display": "0",
                  "context_mapping": {
                    "entity": "layout_builder.entity"
                  },
                  "id": "field_block:node:article:field_image",
                  "formatter": {
                    "type": "image",
                    "settings": {
                      "image_style": "large",
                      "image_link": ""
                    },
                    "third_party_settings": [],
                    "label": "hidden"
                  }
                },
                "additional": [],
                "weight": 0
              },
              "cb54c86f-218e-4243-8a2c-901823ebf81d": {
                "uuid": "cb54c86f-218e-4243-8a2c-901823ebf81d",
                "region": "content",
                "configuration": {
                  "label_display": "0",
                  "context_mapping": {
                    "entity": "layout_builder.entity"
                  },
                  "id": "extra_field_block:node:article:links"
                },
                "additional": [],
                "weight": 3
              },
              "06dbc3f2-a509-42ee-94a4-1bfdafa61017": {
                "uuid": "06dbc3f2-a509-42ee-94a4-1bfdafa61017",
                "region": "content",
                "configuration": {
                  "label_display": "0",
                  "context_mapping": {
                    "entity": "layout_builder.entity"
                  },
                  "id": "field_block:node:article:comment",
                  "formatter": {
                    "type": "comment_default",
                    "label": "above",
                    "settings": {
                      "view_mode": "default",
                      "pager_id": 0
                    },
                    "third_party_settings": []
                  }
                },
                "additional": [],
                "weight": 4
              }
            }
          }
        ]
      ]

#2942975: [PP-1] Expose Layout Builder data to REST and JSON:API

This came up as the daily BSI target

I tried following the steps but I'm not seeing the error. Can you verify if you are seeing it in D11 still? If not we can close out
If still a bug please move back to Active and update the summary.

Thanks.

Since there's been no follow up and can't reproduce going to close out. If still an issue please re-open maybe updating summary with clearer steps?