grub is not installed, even on ext-4 filesystem

[Silvius]

when you install a new system, not mater what kind of partition you use for first primary partition, the grub will be not installed. I tested some configuration, the grub refuse to install.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.4
ProcVersionSignature: Ubuntu 4.15.0-13.14-generic 4.15.10
Uname: Linux 4.15.0-13-generic x86_64
ApportVersion: 2.20.9-0ubuntu2
Architecture: amd64
CasperVersion: 1.392
CurrentDesktop: ubuntu:GNOME
Date: Sat Apr 28 17:54:32 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Beta amd64 (20180404)
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)