function mymodule_views_query_alter(ViewExecutable $view, QueryPluginBase $query) {
  foreach($query->where as &$condition_group) {
    foreach($condition_group['conditions'] as &$conditions) {
      /**
       * my_field_name_value is the Linked Document->media.field_document_tag.target_id (taxonomy term id)
       */
      if($condition['field'] == 'my_field_name') {
        $condition = [
          'field' => 'my_field_name',
          'value' => 'my_field_name_value',
          'operator' => '=',
        ];
      }
    }
  }
}