Update: The NUC with the Celeron J3455 is no longer delivered with Windows 10 Home, but with Windows 10 in S Mode. What exactly that is can be read here: https://www.howtogeek.com/354057...
It is important to note that you can "upgrade" to Windows 10 Home for free - but you have to register in the Microsoft Store.
We simply took a USB stick and installed a clean Windows 10 Home installation, which is activated automatically.
Unfortunately, we do not know whether this also works with Windows 10 Pro. /sa

Ja, Windows 10 Home.