VirtualBox EFI Boot Problem

Due to some special circumstances, SigintOS does not work as EFI boot. You need to turn off the EFI feature when booting the ISO file with VirtualBox.

You will encounter this error when EFI Boot is on.

You can use Settings -> System section to turn off EFI Boot

When you turn off the EFI feature from the settings, you will see this screen with Legacy Boot.