WooCommerce: How to customize the out of stock message1 min read

Add this code to your functions.php file:

add_filter('woocommerce_get_availability_text', 'themeprefix_change_soldout', 10, 2 );

/**
* Change Sold Out Text to Something Else
*/
function themeprefix_change_soldout ( $text, $product) {
if ( !$product->is_in_stock() ) {
$text = '<div class="">Sold out.</div>';
}
return $text;
}

Code courtesy of Storepro.io