Magento – Magento 2: get shipment collection by order

You can get shipments using

$order = Mage::getModel('sales/order')->load($orderId);
$shipments = Mage::getResourceModel('sales/order_shipment_collection')
        ->setOrderFilter($order)
        ->load();

Or

$order = Mage::getModel('sales/order')->load($orderId);
$order->getShipmentsCollection();

Shipment products can be fetch by

foreach($shipments as $shipment){
    foreach ($shipment->getAllItems() as $product){
        echo $product->getName() . "<br/>";
    }
}

Your override file path is incorrect.

You have to just override order_new.html file at below location.

app/design/frontend/[Vendor_Name]/[Theme_Name]/Magento_Sales/email/order_new.html

Clear & Flush the Cache by using below command:-

sudo php bin/magento cache:clean
sudo php bin/magento cache:flush