unable to install grub

[Daniele Lugli]

xubuntu installation from usb stick
Everything fine until grub, which cannot be installed

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: ubiquity 22.04.20
ProcVersionSignature: Ubuntu 6.5.0-18.18~22.04.1-generic 6.5.8
Uname: Linux 6.5.0-18-generic x86_64
NonfreeKernelModules: zfs
ApportVersion: 2.20.11-0ubuntu82.5
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.470.2
Date: Thu Apr 11 19:13:06 2024
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/xubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Xubuntu 22.04.4 LTS "Jammy Jellyfish" - Release amd64 (20240216.1)
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: Error: path contained symlinks.
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)