Grub installation failed on RAID configuration

After Ubuntu 20.04 LTS is DONE, it came a message on the screen, cannot install the bootloader on /dev/sda

Device Start End Sectors Size Type
/dev/sda1 1312768 7604223 6291456 3G EFI System
/dev/sda2 264192 1312767 1048576 512M BIOS boot
/dev/sda3 7604224 467814399 460210176 219.5G Linux filesystem

/dev/sda is the first disk in the RAID5 array

Disk /dev/md0: 438.65 GiB, 470983639040 bytes, 919889920 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 524288 bytes / 1048576 bytes
Disklabel type: gpt
Disk identifier: 3CDC0732-4E24-4828-BC86-85B35CCA53E5

Device Start End Sectors Size Type
/dev/md0p1 2048 411647 409600 200M BIOS boot
/dev/md0p2 976896 128872447 127895552 61G Linux filesystem
/dev/md0p3 128872448 919887871 791015424 377.2G Linux filesystem

Bootloader fails to install on /dev/sda. Also it doesn't work on /dev/sdb and /dev/sdc the other 3 drives from the RAID array.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckMismatches: ./pool/restricted/n/nvidia-graphics-drivers-440/libnvidia-extra-440_440.82+really.440.64-0ubuntu6_amd64.deb
CasperMD5CheckResult: skip
CasperVersion: 1.445
Date: Tue May 5 17:32:18 2020
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed initrd=/casper/initrd quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)