You need to copy related.php file (xstore/woocommerce/single-product folder) to xstore-child/woocommerce/single-product folder and add this code
'meta_query' => array( array ( 'key' => '_stock_status', 'value' => 'instock', 'compare' => '=' ))
https://prnt.sc/jhpa6w
Also, edit xstore-child/woocommerce/single-product/up-sells.php file https://prnt.sc/jhpb65 > https://prnt.sc/jhpc25
$meta_query = array( array ( 'key' => '_stock_status', 'value' => 'instock', 'compare' => '=' ));
Let us know result.
Regards