Hello, Epic Tenno!
Epic Games is aware of an issue that is causing Warframe to crash when selecting full screen mode. Epic Games is working on a fix.
We will update the title and contents of this page as soon as this issue is resolved. Until then, Tenno playing via the Epic Games Store launcher can run the game in windowed mode to avoid the issue. You can launch in windowed mode by disabling fullscreen from the launcher.
Thanks for your patience!
UPDATE! 6:00 PM EST: The fix is