18.04 installer does not allow to choose legacy install when launched from UEFI live session

[mohican]

Due to a limitation of my BIOS I can only boot from a USB-bootable key in EFI mode.

However on my machine the OS must be installed in legacy (BIOS) mode.

When I installed Ubuntu 16.04 from this EFI-booted USB-key, I had warning message from the installer, before choosing the partitioning option that said approximately :

"The microcode has started the installer in UEFI mode but there seem to be other OS installed using the BIOS compatibility mode [...] you can force installation in UEFI mode but you may not be able to start the other OS. If you want to be able to start them you should NOT force installation in UEFI mode."

Then hitting the "Back" button yielded to the partitioning option screen and the installation went on in legacy mode.

But when I tried today to install Ubuntu 18.04 from the downloaded and verified desktop 64 bits ISO, in the same environment, using the same method, there was NO WARNING and therefore in the end of the installation process I had a failure message stating that :
"grub-efi-amd64-signed failed to install to /target/"

The installer failed to detect and to warn that there was other OS already installed in BIOS legacy mode.

[ruben (ubuntu2-a)]

Hello, I also have the same problem that you, I also have an old computer of 2013 with very little possibility of starting, and I also note that if I install ubuntu 18.04 on a hard drive SSD or is already a partition Windows 10, the installation do not want to finish and block on the installation of grub efi amd64, impossible to continue and finish the installation!! I never had this problem with other distribution linux via USB, I tested several keys usb and always the same problem. thus is it impossible to install ubuntu 18.04 on a hard drive already containing an operating system in mode “legacy” could you investigate? Yours sincerely

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.