I have it working now by: In the end, it turned out that it was not directly related to BIOS although I did upgrade to 1.13.0 in the process. Thank you for your assistance.
Hello, I have just bought a Latitude 7400. It had Windows 10 installed but I am a Linux user and I only checked that Windows boots up correctly. As far as I can see, the firmware is updated and configured to boot from the USB drive. However, when I do select the USB drive to boot from through F12, I am greeted with a popup with a title of "Critical Error Message" whose contents is "No bootable devices found". The popup is displayed on a white background with "Dell. SupportAssist | Pre-Boot System Performance Check" at the top. When the popup displays, I can only click a Shutdown button, there is nothing else displayed. Let me also add that I have this thread from Spiceworks and I have tried the disabling of SMM mitigation workaround exactly as it is described over there, to no avail. I hope that I provided all the details necessary and that someone from Dell can help me. Feel free to PM me for the service tag. Thank you.
Latitude 7400 - BIOS 1.13.0 - No bootable devices found