From
https://www.qubes-os.org/doc/thinkpad-troubleshooting/:
Instructions for getting your Lenovo 450 laptop working with Qubes/Linux
Lenovo 450 uses UEFI, so some settings are needed to get Qubes (or Fedora) to boot, otherwise Qubes install USB stick will reboot right after boot selector screen and not continue install.
Setting UEFI options to get Qubes install to boot
Enable Legacy USB mode
Disable all Secure Boot and UEFI options, but leave this enabled: Config / USB / USB UEFI BIOS SUPPORT
Save settings and reboot
Install Qubes
… and now enjoy :) These settings may be needed also in other UEFI computers.
Does this mean the installation will be legacy? I installed via this method (on a T470) and the computer will not begin to boot except in legacy mode.