Why is it impossible to install the Grub start program in the BIOS_Grub partition on a fake-RAID1 ?

[Guillaume Tetart]

Always the same problem,
during the installation of Ubuntu 22.04 on a fake-Raid-1 array, the installation of Grub always fails on the dedicated partition.
My computer is a HP-xw44000, without any UEFI technology. Raid-1 array configured in the Raid bios (ctrl-i).
Could you please explain and show me clearly the solution, if there is one ; I didn't find any suitable response on the the different forum's ...
Regards,

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: ubiquity 22.04.19
ProcVersionSignature: Ubuntu 5.19.0-32.33~22.04.1-generic 5.19.17
Uname: Linux 5.19.0-32-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu82.3
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.470.2
CurrentDesktop: ubuntu:GNOME
Date: Wed Jun 21 18:39:45 2023
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz nomodeset file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 22.04.2 LTS "Jammy Jellyfish" - Release amd64 (20230223)
ProcEnviron:
 LANGUAGE=fr_FR.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 LC_NUMERIC=C.UTF-8
RebootRequiredPkgs: Error: path contained symlinks.
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)