nudge said:
Wrong alert - the problem is mostly in front of the computer

Before creating 'BackgroundAppGlobalToggle' with value 0 my script checks whether the related key exists and creates it if not.

But due to wrong evaluation it ran the statement New-Item -Path HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Search -Force which - I wasn't aware - drops an existing key with ALL properties before creating new.
The properties BingSearchEnabled and CortanaConsent were dropped which were set to 0 just before.
That means: I activated the Bing search inadvertently without noticing.

After adjusting the code the Windows 10 setup works as expected.

I apologize
Nothing to apologize for. I'm just happy you got it sorted out.