Lokalise supports over 400 languages, however you can configure your language ISO code according to your own preferences.
There are two options when changing language codes.
Option 1. Use language settings
If you would like to make a global language code change, use this option.
Navigate to projects dashboard, click the three dots (...) next to the language name and choose Language settings... from the dropdown menu.
Option 2. Use Download settings
You can override the global language code setting for each of the export file formats.
Navigate to the Download project page, select the desired format and adjust the language code in the list on the right side. Once adjusted, click Generate bundle to save the preferences.