Magento – Magento 2: How to Apply Coupon Code based on Product Customizable Option

Duplicate the conditions into the "Apply the rile to cart items matching....".
it clearly states in the title "leave blank for all items".

You can change code in your carrier model file collectRates function check coupon code is applied or not from calling quote object and set custom price if your 8 to 15 days delivery method available and set 0 price for free shipping .

you can get a coupon code from quote object from here

$quote  = $this->session->getQuote();

$address = $quote->getShippingAddress();

$shippingaddress    = $quote->getShippingAddress()->getData();

$coupon     = $quote->getCouponCode();

Before apply this code you have to declare session in construct method like this

protected $session;

public function __construct(

\Magento\Checkout\Model\Session $session, ) {   

$this->session = $session;

}

after then you get quote data from session in magento 2.