Blocksy 2 Change Add to Cart Link with Quickview If Out-of-stock or Backorder

blc-2-open-quickview-when-out-of-stock.php

<?php
add_filter( 'woocommerce_loop_add_to_cart_link', function( $link, $product ) {
    if ( ! $product->is_in_stock() || $product->is_on_backorder() ) {
        return '<button class="ct-open-quick-view ct-button" aria-label="Quick view toggle">Backorder Now</button>';
    }
    return $link;
}, 10, 2 );