The Affinity Publisher Windows customer beta 1.8.0 has all UI locales available.
In the Edit menu > Preferences > General you can choose any of the 10 languages, restart the application and experience Affinity Publisher in that locale.
We are hoping that the localisation is now correct, but if you see any words or phrases that are out of the ordinary, or are clipped/cropped short in the Windows build PLEASE report them in this thread, stating the language and version you are running and what OS you are seeing the problem on.
Use this thread (Do not make new threads) unless you are seeing a bug that does not happen in English, so Bugs in new threads, localisation issues in this thread.
The help file is still out for translation (sorry) but this thread can be used to report anything you see in the software.