https://github.com/unraid/lang-en_US
LOCAL TESTING
Once the translations are complete and you want to test locally the (intermediate) results, the text files need to be zipped into a single ZIP file. Give the ZIP file the name of your language, e.g. French.zip.
In the GUI go to: Tools -> webGUI -> Language (switch to Developer view)
By default only the English language is installed (built-in)
Choose the ZIP file you have created earlier as the source file
If the language name is recognized, it will be automatically selected, otherwise chose the name of the language from the dropdown menu to install.
Click on "Upload" will add your translations to the GUI under the selected language name
NOTE: If your language is not available from the dropdown menu, please make a request on the Unraid forum
Now your language is available for local testing!
In the GUI go to: Settings -> Display Settings -> Language
Select the preferred language from the dropdown menu. Note that only the available language choices are displayed here.