Solution: Windows 10 uses two display languages (at once)

When taking screenshots for a tutorial on how to connect a scale to a network, I came across this curious mixture of both English and German in the network adapter settings:Network adapter properties in German and English

I confirmed that the Windows display language was set to English. I tried  deleting the German language pack, but it did not make a difference: my Windows was still bilingual.

Eventually, I found the solution :

  1. Open to the (legacy) Control Panel, click on Clock, Language and Region, then click on Region.
  2. In the Region dialog, select the Administrative tab.
  3. Click on Copy settings…
  4. You’ll probably see that the Display Language under Current User is not the same as the Display Language under Welcome screen:windows welcome screen and user account settings
  5. This can be fixed by checking the Copy your current settings to: Welcome screen and system accounts checkbox, then clicking on OK:
    windows welcome screen and user account settings monolingual

After restarting, the dialog appeared completely in English:network adapter properties in english