Unable To Boot From Usb
Steve4461 is on the right path. The trouble may be the boot mode you are using. When you created the bootable USB drive with Rufus, it may have been created to boot in BIOS boot mode (MBR). If that is the case, for a 13th generation Dell server; you would need to change your systems boot settings to be in BIOS boot mode in order to boot to that key.
Unable to Boot from USB (AN515-52-50VR) Secure Boot: Disabled. Boot Mode: UEFI Pressing enter on that option only shows UEFI. Boot Mode: UEFI There is only one option for it. 32bit Ubuntu Server 14.04.5. This did not work on the Acer. 64bit Ubuntu Server 14.04.5 LTS amd64. This DOES work. UEFI has feature called safe boot which adds extra layer of security to loader and it prevent booting from external sources like bootable USB Drive or CD. Therefore even you make Bootable flashdrive or CD it won't show up on boot menu or booting process.
That said, you may want to boot to a USB key with the UEFI boot mode. If that is the case, then the you need to create a UEFI bootable USB key. Even if you know that your ISO supports both boot methods, your bootable drive/media will dictate what boot method you need to use to get to that ISO. With 12th generation server we had the option of a one time boot option from the boot manager. It worked better for these situations than 13th Gen does in my opinion. For instance, when I have a BIOS bootable USB key, I haven't been successful using the 13th Gen one time BIOS boot option when in UEFI boot mode. I have had to change the boot mode to BIOS mode to use said key.
Hope this helps. In your case, if you need your boot method to be UEFI and subsequent partition scheme to be GPT, just create an EFI bootable key, stay in UEFI boot mode, and then go through the LifeCycle Controller to load your OS. In Rufus, there is an option to use both BIOS and UEFI schemes. If that option doesn't work, again, just use the UEFI version only scheme and see if that works better for you.
Let me know how it goes. If the server isn't booting to the USB at all try moving the stick to a USB2 interface (typically in back). This is a common problem with USB booters in that some USB3 interfaces won't boot from them. If you image a lot of laptops from USB sticks you quickly learn to avoid the pretty blue USB3 interfaces and stick to the black ones.Try different USB booter made from different software. Also verify the USB stick actually boots on a workstation or something. They break easily and the creation process isn't always perfect. Steve4461 is on the right path.
The trouble may be the boot mode you are using. When you created the bootable USB drive with Rufus, it may have been created to boot in BIOS boot mode (MBR). If that is the case, for a 13th generation Dell server; you would need to change your systems boot settings to be in BIOS boot mode in order to boot to that key. That said, you may want to boot to a USB key with the UEFI boot mode. Hoi4 paratroopers not working. If that is the case, then the you need to create a UEFI bootable USB key.
Can T Boot From Usb
Even if you know that your ISO supports both boot methods, your bootable drive/media will dictate what boot method you need to use to get to that ISO. With 12th generation server we had the option of a one time boot option from the boot manager. It worked better for these situations than 13th Gen does in my opinion. For instance, when I have a BIOS bootable USB key, I haven't been successful using the 13th Gen one time BIOS boot option when in UEFI boot mode.
I have had to change the boot mode to BIOS mode to use said key. Hope this helps. In your case, if you need your boot method to be UEFI and subsequent partition scheme to be GPT, just create an EFI bootable key, stay in UEFI boot mode, and then go through the LifeCycle Controller to load your OS. In Rufus, there is an option to use both BIOS and UEFI schemes. If that option doesn't work, again, just use the UEFI version only scheme and see if that works better for you.
Let me know how it goes.