installation 20.04 crashed while installing GRUB

[Guido Buitendijk]

Installing over 18.04.14, using the two /sda's it was using.
Boot doesn't work, get grub rescue.
The found fixes didn't work as well.
Boot again from flash-drive, re-install 20.04 over previous 20.04 (yes, 18.04 no longer present).
The drive also houses sda2, sda3, sda4 which are backups of partitions from a former harddrive + a Windows10 partition.

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
CasperMD5CheckResult: pass
CasperVersion: 1.445
Date: Mon May 4 13:28:38 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Guido Buitendijk (gbuitend)]

!UpgradeStatus! The previous Ubuntu version was the 32-bits version of 18.04, so that's why there is no upgrade log, it was indeed a fresh install to make the switch to 64-bits.