Ubiquity failed to intall grub during 20.10 install

[Damon Lynch]

Installation of grub 2.0 to /dev/sda failed (why I don't know). The bootloader for Ubuntu 20.04 (installed in another partition) was already present.

Machine is 2011 era Lenovo W520 w/ SSD (sda) & HDD (sdb).

Ubuntu 20.10 installer is from Oct 16 daily ISO.

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: ubiquity 20.10.11
ProcVersionSignature: Ubuntu 5.8.0-23.24-generic 5.8.14
Uname: Linux 5.8.0-23-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu50
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.452
CurrentDesktop: ubuntu:GNOME
Date: Fri Oct 16 19:27:36 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.10 "Groovy Gorilla" - Beta amd64 (20201016.1)
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:
 linux-image-5.8.0-23-generic
 linux-base
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)