If the user agent of your browser is seen as a Linux OS, Microsoft let you download the iso:

 

With Firefox, you can use this extension then go to this URL : https://www.microsoft.com/en-US/software-download/windows10ISO

 

Correct. That's the trick the ISO downloader is basically working with (plus replacing the Win 10 product ID for other product IDs such as Win 7 or Office 2010, and inserting product keys for software that can't be downloaded without authentication).

Good to know.

So for users who want to download Windows 10 but can't use the ISO downloader, we can now redirect them to this thread.

I'll add it to the FAQ at the next convenient opportunity.