grub install failed when trying minimL install option from ubiquity on a multi drive system tried installing grub on sdb

[darkone778]

booted system into live usb environment to install. Went and chose minimal option for install to a external USB hdd system runs install, gets to installing grub comes up with reported error, chose a different drive on the machine besides sdb and grub does not install on either the internal hdd or nvme drive what so ever

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.9
ProcVersionSignature: Ubuntu 4.15.0-15.16-generic 4.15.15
Uname: Linux 4.15.0-15-generic x86_64
ApportVersion: 2.20.9-0ubuntu6
Architecture: amd64
CasperVersion: 1.393
CurrentDesktop: ubuntu:GNOME
Date: Sat Apr 21 09:29:46 2018
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180421)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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

[Phillip Susi (psusi)]

You booted the installer in bios mode but appear to be trying to install to a disk that is set up to boot in UEFI mode. You need to boot the installer in UEFI mode.