installer crashed at grub step, LG gram 2021 17

[Kristopher J Rodak]

this was a re-install on a win 10 dual boot. Grub had vanished and ubuntu became un-bootable. so I was installing ubuntu 20.04.02 over itself. The installation appeared to be complete, but failed at the grub installation step. The "Restart Now" dialog was visible. Hardware is LG gram 17 2021 with default bios settings, e.g. secure boot not disabled, etc. Boot order did have ubuntu first, and the grub menu was working until I booted into win 10. after that, it booted directly into win 10. When I used F10 to get to the boot menu, ubuntu was there in the top position, but it would not boot.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.10
ProcVersionSignature: Ubuntu 5.8.0-43.49~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-43-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
CurrentDesktop: ubuntu:GNOME
Date: Mon Aug 16 11:48:04 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)