How can customers cancel their orders in Magento 2 frontend?

My friend wants to allow his customers to cancel their Pending orders by themselves, he feels very inconvenient when he has to cancel them by default.
thanks in advance

You can try Cancel Order By Customer Magento 2 extension. It allows the user to cancel the order easily from the front end. The store owner can set custom mail template from admin side for cancel order. The customer can also add comment when cancel order.

Magento 2 Auto Cancel Order extension
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Magento 2 Auto Cancel Order extension allows your Magento 2 store to to cancel pending and pending payment order automatically.

• Cancel order automatically after a period.
• Choose cancellation time for other payment methods
• Re-stock product of the canceled order

For further information such as demo site, support policies and buying this extension, please visit BSSCommerce Magento 2 Auto Cancel Order extension.

Magento 2 Cancel Order by Meetanshi allows customers to cancel their pending order from the storefront.

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The competition in E-commerce business is all about offering the best customer experience. For Magento 2 stores, Meetanshi's Magento 2 Cancel Order extension helps in improving the shopping experience of the store.

With Magento 2 Cancel Order by Customer extension, let customers cancel their pending orders from "My Account", "My Orders" and order details page in the frontend. The admin is notified via an automated Email about the order cancelation.

The Magento 2 Cancel Order extension also lets customers add comments in the confirmation popup that can be seen from the backend. It gives useful data to the admin for improving the products' features and understanding the customers' mindset!

Benefits of Magento 2 Cancel Order:

* Let customers cancel their pending orders from "My Account", "My Orders" and order details page in the storefront.
* Allow customers to add comments in the confirmation popup that appears while canceling the orders. 
* The admin is notified via an automated Email when a customer cancels the order from the storefront.
* Admin can choose the notification Email template, sender, and receiver.
* Option to set custom text for the button label and the notice text in the popup.
* When a customer cancels the order, its status is changed from "Pending" to "Cancel" and the product is restocked.
* Enhanced shopping experience.
* Customer convenience for order cancelation.

For more information, visit https://meetanshi.com/magento-2-cancel-order.html