Order receipt e-mail language for guest checkout Is there a way to have the order receipt e-mail be in the language of the site version that was used for placing the order?

The order receipt e-mail that gets sent out (content of commerce-order-receipt.html.twig) for a guest is currently always in the default language. That means a user would order items from the French site, and get an English confirmation. It appears that no language data is saved for an order, so I guess there's no built-in way to do this. 

Does anyone have any ideas?
This is a known problem. Orders need a language field.

That will be added as a part of https://www.drupal.org/project/commerce/issues/2603482