Woocommerce sort products by multiple meta keys

Question

I'm adding extra sorting options for products, like by sku, or stock status. It works, but I would like to have a sorting result by multiple meta keys: all the products in stock must appear before the out of stock ones, but I need them sorted by sku too.

I've found several functions both using woocommerce_get_catalog_ordering_args and woocommerce_product_query, but none of them seems working. I only get a sorting by _sku OR by _stock_status, never combined.

Any code working with the latest woocommerce version?

actual code:

add_filter('woocommerce_get_catalog_ordering_args', 'sort_products_by_stock_order');
function sort_products_by_stock_order($args) {

    // in-stock filter and default
    if(!isset( $_GET['orderby'] ) || ( isset( $_GET['orderby'] ) && 'in-stock' === $_GET['orderby'] )) {
        $args['meta_key'] = '_stock_status';
        $args['orderby'] = array( 'meta_value' => 'ASC' );

    // SORT BY SKU
    } else  if( isset( $_GET['orderby'] ) && 'sku' === $_GET['orderby'] ) {
        $args['meta_key'] = '_sku';
        $args['orderby'] = array( 'meta_value' => 'ASC' ); 
    
    }
    
    return $args;
}

Thanks