Get a list of entities that reference a paragraph type.

check_paragraph_usage.php

_field_usage_check('event', 'entity_reference');
/**
 * string $reference_type
 *   Example: 'node' or 'paragraph'
 * string $referenced_entity_type
 *   Example: 'entity_reference' or 'entity_reference_revisions'
 *
 * Given the machine name of a paragraph, return/print the entities that reference it.
 */
function _field_usage_check($referenced_entity_type, $reference_type) {
  $map = \Drupal::service('entity_field.manager')->getFieldMap();
  foreach ($map as $entity_type => $entity_type_array) {

    foreach ($entity_type_array as $field_name => $field_data) {

      if (str_starts_with($field_name, 'field_') && $field_data['type'] == $reference_type) {

        $parent_bundles = $field_data['bundles'];
        foreach ($parent_bundles as $parent_bundle_key => $parent_bundle_name) {

          $field_config_string = sprintf('field.field.%s.%s.%s', $entity_type, $parent_bundle_name, $field_name);
          $bundles = \Drupal::config($field_config_string)
            ->get('settings.handler_settings.target_bundles');

          $x = is_array($bundles);
          $y = is_object($bundles);
          foreach ($bundles as $child_bundle_key => $child_bundle_name) {

            if ($child_bundle_name == $referenced_entity_type) {
              dump( $entity_type  . ' - ' . $parent_bundle_name  . ' - ' . $field_name);
            }
          }
        }
      }
    }
  }
}