Append custom content for a specific post type

searchwp-customizations.php

<?php

// Customize SearchWP result entry data for the SearchWP template.
add_filter( 'searchwp\results\entry\data', function( $data, $result ) {

    if ( $result instanceof \WP_Post && $result->post_type === 'product' ) {
        $data['content'] .= '<p>Free delivery available!</p>';
    }
    return $data;

}, 20, 2 );