grub-installer failed during a re-install of bionic beaver 18.04

[Quentin Pascal]

After a first installation in dualboot with Windows10 and two weeks of Linux use and some updates, I lost grub-menu and Ubuntu18.04 refused to start even from the uefi entry in the bios boot menu. So I tried to reinstall the root partition (ext4, formatted, 21 Gb), keeping "/Home" partition. Finally grub installation missed.

Description: Ubuntu 18.04.1 LTS
Release: 18.04
Linux ubuntu 4.15.0-29-generic

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.6 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CasperVersion: 1.394
Date: Mon Nov 26 15:50:20 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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