WooCommerce hide shipping rates when free shipping is available, but allow local pickup if the order qualifies for free shipping

woo_shipping_functions.php

<?php

/**
 * Hide shipping rates when free shipping is available, but allow local pickup if the order qualifies for free shipping.
 *
 * @param array $rates Array of rates found for the package.
 * @return array
 */
function woo_hide_shipping_when_free_is_available( $rates ) {
    $free = array();
    $allowed_methods = array(); // Array to store allowed methods (free shipping + local pickup)

    foreach ( $rates as $rate_id => $rate ) {
        if ( 'free_shipping' === $rate->method_id ) {
            $free[ $rate_id ] = $rate;
        }
    }

    // If free shipping is available, allow it and also keep local pickup
    if ( ! empty( $free ) ) {
        foreach ( $rates as $rate_id => $rate ) {
            if ( 'local_pickup' === $rate->method_id ) {
                $allowed_methods[ $rate_id ] = $rate;
            }
        }
        return array_merge( $free, $allowed_methods );
    }

    return $rates; // If free shipping is not available, return all shipping methods
}
add_filter( 'woocommerce_package_rates', 'woo_hide_shipping_when_free_is_available', 100 );