Symfony serializer: removing fields after normalization

Question

After upgrading to Api platform 2.6, the non ApiResource entities started being serialized (ld-json) along with a fake identifier and their type. For example:

{
  "@type": "MetaData",
  "@id": "_:11294",
  "id": "bf1e417c-27ff-48c1-a591-40e5a43c708c",
  "key": "key1",
  "value": "value1"
}

we would like to remove these fields. To do so I've tried to implement a custom normalizer hoping to be able to hook in after the object is transformed in array and before the array is converted to a json.

Looking at the registered normalizers:

 ----------------------------------------------------------- ---------- --------------------------------------------------------------------------- 
  Service ID                                                  priority   Class name                                                                 
 ----------------------------------------------------------- ---------- --------------------------------------------------------------------------- 
  api_platform.serializer.normalizer.item                     -895       ApiPlatform\Core\Serializer\ItemNormalizer                                 
  api_platform.problem.normalizer.constraint_violation_list   -780       ApiPlatform\Core\Problem\Serializer\ConstraintViolationListNormalizer      
  api_platform.hydra.normalizer.collection_filters            -985       ApiPlatform\Core\Hydra\Serializer\CollectionFiltersNormalizer              
  api_platform.hydra.normalizer.error                         -800       ApiPlatform\Core\Hydra\Serializer\ErrorNormalizer                          
  api_platform.hydra.normalizer.entrypoint                    -800       ApiPlatform\Core\Hydra\Serializer\EntrypointNormalizer                     
  api_platform.hydra.normalizer.constraint_violation_list     -780       ApiPlatform\Core\Hydra\Serializer\ConstraintViolationListNormalizer        
  api_platform.hydra.normalizer.documentation                 -800       ApiPlatform\Core\Hydra\Serializer\DocumentationNormalizer                  
  api_platform.jsonld.normalizer.object                       -995       ApiPlatform\Core\JsonLd\Serializer\ObjectNormalizer                        
  api_platform.swagger.normalizer.api_gateway                 -780       ApiPlatform\Core\Swagger\Serializer\ApiGatewayNormalizer                   
  api_platform.openapi.normalizer.api_gateway                 -780       ApiPlatform\Core\Swagger\Serializer\ApiGatewayNormalizer                   
  api_platform.serializer.uuid_denormalizer                              ApiPlatform\Core\Bridge\RamseyUuid\Serializer\UuidDenormalizer             
  serializer.denormalizer.array                               -990       Symfony\Component\Serializer\Normalizer\ArrayDenormalizer                  
  serializer.normalizer.object                                -1000      Symfony\Component\Serializer\Normalizer\ObjectNormalizer                   
  serializer.normalizer.problem                               -890       Symfony\Component\Serializer\Normalizer\ProblemNormalizer                  
  serializer.normalizer.json_serializable                     -900       Symfony\Component\Serializer\Normalizer\JsonSerializableNormalizer         
  serializer.normalizer.datetime                              -910       Symfony\Component\Serializer\Normalizer\DateTimeNormalizer                 
  serializer.normalizer.data_uri                              -920       Symfony\Component\Serializer\Normalizer\DataUriNormalizer                  
  serializer.normalizer.dateinterval                          -915       Symfony\Component\Serializer\Normalizer\DateIntervalNormalizer             
  serializer.normalizer.datetimezone                          -915       Symfony\Component\Serializer\Normalizer\DateTimeZoneNormalizer             
  serializer.normalizer.constraint_violation_list             -915       Symfony\Component\Serializer\Normalizer\ConstraintViolationListNormalizer  
  api_platform.problem.normalizer.error                       -810       ApiPlatform\Core\Problem\Serializer\ErrorNormalizer                        
 ----------------------------------------------------------- ---------- --------------------------------------------------------------------------- 

the closest I've got was around the api_platform.jsonld.normalizer.object however if the priority I use is -994, I get the original object, if I use -996 I get the single string/boolean/numeric fields (so after the normalization).

Is there any way I can get the associative array so that I can remove @id and @type if @id starts with _:?

The line of the code that adds those properties seems to be this however that probably just adds to the context it doesn't include those fields in the normalized array.