Problem

If you’re installing Shopware from the Production Template (like I did), and follow the installation instructions closely, you will end up with a store that uses English as the default language. While this might be perfectly fine if you have all of your content in English language, it will be most likely a problem if your Ecommerce business requires a different langauge.
Neither during the creation of the environment file nor during the database creation Shopware 6 asks you, which default language you want to use. And unfortunately, Shopware 6 does not allow you to change that language in the backend at a later time. Given the fact that Shopware is being mostly used in German-speaking countries as well in the rest of Europe, you probably want to change that behaviour from the start.

So to fix that and in order to have Shopware 6 take your preferences into account, you have two options:

Solution 1:

After the creation of the .env file with bin/console system:setup do not continue with the bin/console system:install command which creates the DB, but open your websites’ URL in the browser instead. You will be redirected to yourwebsite.com/recovery/install and Shopware presents you with the web installer. Here you can actually choose the default language.

Solution 2:

After the creation of the .env file with bin/console system:setup do not continue with the bin/console system:install command which creates the DB, but run the following command in your shell

php vendor/shopware/recovery/Install/index.php

This CLI command will start an interactive shell prompting you for various site settings including the default language. The expected input isn’t quite clear always and not a 100 percent intuitive. For example when choosing the default country the default value is GBR (Great Britain), which actually hints you to the excepted 3 digit ISO code. So in order to switch to Germany you need to enter DEU.