Hirsute daily grub-install failure

[Earl]

After being unable to do a fresh install to two different USB3 sticks, I tried using a external USB3 2.5 inch hard disk. The 2 sticks installed a EFI FAT16 partition quickly, but the ext4 format was so slow it did not finish even until the next morning.

The external HDD formatted quickly, but the installer was not able to install grub and terminated in failure.

Since 2 weeks, I have not been able to accomplish a fresh install of Hirsute daily to either external USB sticks or hard disks.

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: ubiquity 21.04.14
ProcVersionSignature: Ubuntu 5.11.0-13.14-generic 5.11.7
Uname: Linux 5.11.0-13-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu62
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.461
Date: Tue Apr 13 11:35:29 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu-mate.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu-MATE 21.04 "Hirsute Hippo" - Beta amd64 (20210412)
RebootRequiredPkgs:
 linux-image-5.11.0-13-generic
 linux-base
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Earl (2104-amdgpu)]

13 April
partial success. Deleted ext partions on HDD and restarted with a 100MB FAT32 partition followed by ext4 partitions for / and for /home. Told the installer to use the FAT32 partition for EFI with boot,esp flags.
This test was a total success resulting in a functioning, bootable Hirsute external USB hard disk.

Now, will continue the test with USB sticks again to see if a full install to USB memory sticks is possible.

[Earl (2104-amdgpu)]

13 April_2nd
Even with a high-quality big-name USB stick, a Hirsute full install was not possible.

Executing 'grub-install /dev/sdd' failed. This is a fatal error.

Will try again using different method.

[Earl (2104-amdgpu)]

14 April_3rd

No matter how I try, I am unable to do a full install to a USB3 memory stick.

In contrast to yesterday, I was not able to do a full install to a 2nd external USB hard disk of the same make and model as yesterday. The usual error msg
Executing 'grub-install /deb/sdb' failed. This is a fatal error.

Will continue trying to do a Hirsute full install for each daily and report back.

[Earl (2104-amdgpu)]

14 April_4th

Hirsute build 14 April
Trying to do a full install to a USB3 stick:

Executing 'grub-install /dev/sdb' failed. This is a fatal error.

Will continue trying to do a Hirsute full install for each daily and report back.

[Earl (2104-amdgpu)]

After the release of 22 April, the grub-install bug appears to be solved. I do not know how to close this bug report.