Drupal 8/9 - Add new properties to a field type

MYMODULE.install

/**
 * Add new property to all fields of type FIELD_TYPE.
 */
function MYMODULE_update_8001() {
  $field_type = 'FIELD_TYPE'; // ID of the FieldType you are updating
  $new_properties = [
    'FIELD_NAME' => [ // Field name should match the name in the schema
      'description' => 'FIELD_DESCRIPTION', // Give your field a description
      'type' => 'FIELD_TYPE', // @see: https://www.drupal.org/docs/7/api/schema-api/data-types/data-types-overview
    ]
  ];

  $definition_update_manager = \Drupal::entityDefinitionUpdateManager();
  /** @var \Drupal\Core\Entity\EntityFieldManagerInterface $field_manager */
  $field_manager = \Drupal::service('entity_field.manager');
  /** @var \Drupal\Core\Entity\EntityTypeManager $entity_type_manager */
  $entity_type_manager = \Drupal::service('entity_type.manager');
  $field_map = $field_manager->getFieldMapByFieldType($field_type);
  $schema = \Drupal::database()->schema();
  foreach ($field_map as $entity_type_id => $fields) {
    $field_manager->clearCachedFieldDefinitions();
    $storage_definitions = $field_manager->getFieldStorageDefinitions($entity_type_id);

    $storage = $entity_type_manager->getStorage($entity_type_id);
    /** @var \Drupal\Core\Entity\Sql\DefaultTableMapping $table_mapping */
    $table_mapping = $storage->getTableMapping();

    foreach ($fields as $field_name => $field) {
      $storage_definition = $storage_definitions[$field_name];
      if (!empty($storage_definition)) {
        $column_names = $table_mapping->getColumnNames($field_name);
        $table_names = [$table_mapping->getFieldTableName($field_name)];

        if ($storage_definition->isRevisionable()) {
          $table_names[] = $table_mapping->getDedicatedRevisionTableName($storage_definition);
        }

        foreach ($table_names as $table_name) {
          foreach ($new_properties as $property_name => $property_spec) {
            if (!$schema->fieldExists($table_name,
              $column_names[$property_name])) {
              $schema->addField($table_name, $column_names[$property_name],
                $property_spec);
            }
          }
        }
        $definition_update_manager->updateFieldStorageDefinition($storage_definition);
      }
    }
  }
}