/vendor/magento/module-sales-rule/view/frontend/layout/checkout_cart_index.xml

Take below code from above file

 <item name="discount" xsi:type="array">
	 <item name="component" xsi:type="string">Magento_SalesRule/js/view/cart/totals/discount</item>
	 <item name="config" xsi:type="array">
		<item name="title" xsi:type="string" translate="true">Discount</item>
	 </item>
 </item>

Insert it in overrided checkout_cart_index.xml file of module-checkout.

Now you can see discount their.