I have Ubuntu 16.04 installed on a Dell 5470. I want to reinstall it due to some reasons. I want to boot from USB to reinstall Ubuntu. The problem is, I cannot access the BIOS and the boot menu due to Secure Boot. When I press F2 or F12 during startup the computer still boots into Ubuntu.
systemctl reboot --firmware-setup but I receive
Cannot indicate to EFI to boot into setup mode: Operation not supported How can I boot from USB and reinstall Ubuntu?