Translate shipment tracking message with Polylang Pro and WooCommerce Shipment Tracking Plugin: https://www.pluginhive.com/product/woocommerce-shipment-tracking-pro/

functions.php

add_filter('wf_custom_tracking_message', 'update_tracking_message', 10, 3);

function update_tracking_message($current_msg, $language, $order) {

    global $wpdb;
    $qry = "SELECT term_taxonomy_id FROM {$wpdb->prefix}term_relationships WHERE object_id = $order->ID ORDER BY object_id DESC";
    $values = $wpdb->get_results($qry, ARRAY_A);
    $post_lang_choice = 'en';
    if (!empty($values)) {
        $land_id = $values[0]['term_taxonomy_id'];
        $qryl = "SELECT slug FROM {$wpdb->prefix}terms WHERE term_id = $land_id ";
        $valuesl = $wpdb->get_results($qryl, ARRAY_A);
        if (!empty($valuesl))
            $post_lang_choice = $valuesl[0]['slug'];
    }
    if ($post_lang_choice == 'fr') { 
        //change your language here if needed, for German can use 'de'
        return "Votre commande a été expédiée le [DATE] via [SERVICE]. Pour suivre les envois, veuillez suivre le lien correspondant aux numéros d'expédition [ID]";
    } else {
        return "Your order was shipped on [DATE] via [SERVICE]. To track shipment, please follow the link of ID(s) [ID]";
    }
}