The UFEI does not show an option for a DVD or Thumb Drive as boot options, Only disk and Windows boot manager. Not even a working SSD. Instructions in Dell note: https://www.dell.com/support/article/us/en/19/sln142679/how-to-enable-boot-from-dvd-option-with-uefi-boot-mode-enabled-windows-10-81-8-?lang=en show a list that includes DVD, etc. When I tried to add one following instructions results in "File path or name not found". Question remains how to add a boot device to a Dell XPS8900