After installing the testing release, I found that the language was different from the one I selected at the start of the installation dialog. The language had become the (default) language of the selected location instead. In my case: I prefer the Dutch language but I’m living in France. Selecting Dutch during install does not ‘stick’ if I then choose to set my location to France.
Same goes for the input source. My keyboard was set to US international (QWERTY) during installation but after installation, it was suddenly French (AZERTY) which – if you’re not aware of it – will prevent login in due to a wrong password.
I wonder what would happen if I had lived in Switserland where there are three languages possible ;)
Anyway, how to change the language to Dutch now? If I go to the Gnome setting panel and choose “Pays & langue”, I can only select French. There are no other languages available. How to install them?