Hoping someone can help me before i send these machines back to Dell.

Brand new 5260 AiO.  First Dell BIOS I've seen where you cannot access the internal HDD/SSD through legacy BIOS boot options, but should be fine.  Or so I thought....

BIOS is set to UEFI.  Secure boot is switched off legacy ROM options enabled so I can press F12 and boot from USB to install OS

Trying to do a core, security baseline build of Windows 10 Pro.  Deleted all existing partitions.  Booted from a Rufus win 10 ISO bootable USB key.  shift+f10 diskpart > set disk to GPT and all that jazz.  Installed Windows 10.  Remove USB key and restart.

No bootable devices found....

Go into BIOS.  Notice that under UEFI that Windows Boot Manager is not there.  Nothing, nada. zero.  Click "Add Option" button and get error "File System not found!"

**bleep**!?