您可以尝试自定义_meta_or_tax 中的参数WP_Query （PHP 5.4以上）：

$args = [
    \'post_type\'    => \'post\',
    \'_meta_or_tax\' => true,        // <-- our new custom parameter
    \'tax_query\'    => [...],       // <-- our tax query
    \'meta_query\'   => [...],       // <-- our meta query
];

$query = new WP_Query( $args );

/**
 * Modify WP_Query to support \'meta_or_tax\' argument
 * to use OR between meta- and taxonomy query parts.
 */
add_filter( \'posts_where\', function( $where, \\WP_Query $q )
{
   // Get query vars
   $tax_args    = isset( $q->query_vars[\'tax_query\'] ) 
       ? $q->query_vars[\'tax_query\'] 
       : null;
   $meta_args   = isset( $q->query_vars[\'meta_query\'] ) 
       ? $q->query_vars[\'meta_query\'] 
       : null;
   $meta_or_tax = isset( $q->query_vars[\'_meta_or_tax\'] ) 
       ? wp_validate_boolean( $q->query_vars[\'_meta_or_tax\'] )
       : false;

   // Construct the "tax OR meta" query
   if( $meta_or_tax && is_array( $tax_args ) &&  is_array( $meta_args )  )
   {
       global $wpdb;

       // Primary id column
       $field = \'ID\';

       // Tax query
       $sql_tax  = get_tax_sql(  $tax_args,  $wpdb->posts, $field );

       // Meta query
       $sql_meta = get_meta_sql( $meta_args, \'post\', $wpdb->posts, $field );

       // Modify the \'where\' part
       if( isset( $sql_meta[\'where\'] ) && isset( $sql_tax[\'where\'] ) )
       {
           $where  = str_replace( 
               [ $sql_meta[\'where\'], $sql_tax[\'where\'] ], 
               \'\', 
               $where 
           );
           $where .= sprintf( 
               \' AND ( %s OR  %s ) \', 
                substr( trim( $sql_meta[\'where\'] ), 4 ), 
                substr( trim( $sql_tax[\'where\']  ), 4 )
           );
        }
    }
    return $where;
}, PHP_INT_MAX, 2 );