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Windows 10 setup automatically detects the edition type of a previously  installed Windows version in your computer and then it installs the  corresponding edition of Windows 10.

To avoid this, follow the instructions below:

  • Forcing the installation of a specific Windows version
  • Forcing the selection of a specific Windows version

Copy the ei.cfg file to the sources folder on the desired installation media (USB stick / ISO).

Boot from the desired installation media....

Result:


Source:

https://www.askvg.com/fix-cant-select-windows-10-pro-edition-during-clean-installation/