On the "Sign in" page, use these steps:
Put the laptop in Airplane mode - or do not connect to WiFi or with a cable.
When prompted to sign into a Microsoft account, use the "Shift + F10" keyboard shortcut to open Command Prompt (or Shift + Fn + F10 on some laptops).
Type the following command to release the current network configuration and press Enter: oobe\bypassnro
Quick note: The command is a single phrase without spaces.
Computer will boot automatically, and you may need to start the out-of-box experience again.
Click the "I don't have internet" option.