How does the OFW decide which language to use?

I have EN 00000000 and DE 00000001 audio folders and it seems to be using the DE now but I also remember it using EN at some point. Where is this configured? Can it be changed via teddycloud?

The language is set via the AP configuration of the box. So if you are entering a new WiFI you select the language on the webinterface.

In one of the flash files (could be settings.cfg) there is a default language set if you factory reset the box.