There's another option to download the ISOs from Microsoft. You just have to either use a non-Windows PC (Linux, Mac, Android, whatever...) or use a user-agent spoofer tool so Microsoft's website thinks you're not in Windows. I used this one for Chrome: https://chrome.google.com/webstore/detail/user-agent-switcher-for-c/djflhoibgkdhkhhcedjiklpkjnoahfmg
The reason is that if they see you use Windows they'll offer you their downloader EXE, which can only download to drive C: and if it's full (which is usual when using a small SSD drive as the main one) you can't download even if you have a secondary drive with several free TBs, since you can't choose another drive.
If their site thinks you're not on Windows, they'll offer you direct download links to the ISOs valid for 24h.
The URL to get the ISOs is this one (remember to use a spoofer or a non-Windows device or you won't be able to get the links to the ISOs from this page, and will get links to the tool instead):