Install Ubuntu 20.10 crash at grub-install /dev/sda

[marcello]

Installing Ubuntu 20.10 from USB Live failed at gru-install /dev/sda!
I think problem has to do with UEFI/Legacy installation type.
My system has already Windows 10 installed on /dev/sda2 and ubuntu 20.04 on /dev/sda7 in legacy mode, even if my system BIOS seems to support UEFI mode, I never used it!
After the error if I open a terminal and try to enter command "grub-install /dev/sda" it return:
ubuntu@ubuntu:/$ grub-install /dev/sda
Installing for x86_64-efi platform.
grub-install: error: cannot find EFI directory.

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: ubiquity 20.10.13
ProcVersionSignature: Ubuntu 5.8.0-25.26-generic 5.8.14
Uname: Linux 5.8.0-25-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu50
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.455
CurrentDesktop: ubuntu:GNOME
Date: Mon Oct 26 15:12:35 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.10 "Groovy Gorilla" - Release amd64 (20201022)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 LC_NUMERIC=C.UTF-8
RebootRequiredPkgs:
 linux-image-5.8.0-25-generic
 linux-base
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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

[marcello (genafi)]

I think this is a possible duplicate of
https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1893964

[Vineet Billorey (vineetbillorey)]

Instead, I installed Mint20.1, and its working fine.