ubuntu 20.04.1 lts grub

[Léo Brunet]

Hello dear developers,

Thank you so much for helping me.
I am a total noob. I wanted to make my ASUS K73S old laptop work on ubuntu (on dual boot because I still need some software on windows10) because I am amazed by the free-internet philosophy. It has been a long time since I want to do the first step, now I did it following a youtube tutorial video of TECH_SAMA. I think that I followed exactly what he said, though around the end of the installation process an error message appears :
I try a translation in english (I am french) :
"The grub-efi-amd-signed package failed to install in /target/
in absence of the GRUB programm, the installed programm can't start"
The tutorial video is recent, and so I downloaded the last relase of UBUNTU version 20.04.1 LTS

I found on the web a lot of tutorials explaining how to fix it, but not speaking of the ubuntu 20.04.1 LTS version. The techniques I tried were to partition the free space with a "swap" an "efi" and a "root" partition. (actually that was the first SAMA_TECH was also showing, but it still doesn't work with my laptop apparently. I always get the "grub-efi-amd-signed package failed to install in /target/"
And now I can't even boot on windows10 anymore.

Now when starting the laptop normally (not in Bios mode) I get a black screen written on it :
error '/boot/grub/i386-pc/.mod'
For this also I tried to follow tutorials, but at some point it is not happenning what is suppose to happen and I don't succeed.

thank you thank you thank you for helping !

We also need:

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.2
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
CurrentDesktop: ubuntu:GNOME
Date: Sun Oct 4 14:46:40 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
ProcEnviron:
 LANGUAGE=fr_FR.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)