PHP 7.3 reaches end of support in December 2021 and Adobe Commerce 2.3.x reaches end of support in April 2022. You may want to consider planning your upgrade now to Adobe Commerce 2.4.x and PHP 7.4.x to help maintain PCI compliance.
AdvancedCheckout
Magento\AdvanceCheckout extends Magento_Checkout with following functions: adding product to cart by entering SKU on frontend, uploading list of SKUs to add products to cart on frontend and ability for admin to manage customer’s shopping cart.