尝试以下操作：

function my_custom_ordering( $query ) {
    if($query->is_main_query() AND !is_admin() ) {
      if ( $query->is_home() ||  $query->is_category() ||  $query->is_tag() ){
            $query->set( \'orderby\', \'modified\' );
       }
   }
}
add_action( \'pre_get_posts\', \'my_custom_ordering\' );

function orderby_modified_posts( $query ) {
    if($query->is_main_query()) {
            $query->set( \'orderby\', \'modified\' );
       }
}
add_action( \'pre_get_posts\', \'orderby_modified_posts\' );

<?php
function modified( $query )
{
    if ( $query->is_main_query() && ( $query->is_home() || $query->is_search() || $query->is_archive() )  )
    {
        $query->set( \'orderby\', \'modified\' );
        $query->set( \'order\', \'desc\' );
    }
}
add_action( \'pre_get_posts\', \'modified\' );

?>