Hi all,
I’m pretty new to Unraid but got the same issue on my Dell Server T710.
make things short: UEFI… Forget about that..
That‘s how it worked on my Server to autoboot from USB:
Set to Bios.
USB Device setting from Auto to Harddisk.
Set Bootorder to USB and then Raid.
Save and Reboot.
Server starts with Unraid without manual F11 etc…
Hope that works for you too!
Rauti