install-grub failed, fatal error, on system with SSD and HHD and with Windows 10 installed

[Simon Michelini]

I am trying to install Ubuntu 20.4 alongside Windows 10. Windows is installed on a SSD. There is also a HDD. The installer does not detect the Windows installation. Any way I try to do it I get the same error, that install-grub failed.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.2
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckMismatches: ./pool/main/m/mesa/mesa-vdpau-drivers_20.0.8-0ubuntu1~20.04.1_amd64.deb
CasperMD5CheckResult: skip
CasperVersion: 1.445.1
CurrentDesktop: ubuntu:GNOME
Date: Sat Jan 16 21:55:27 2021
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash nomodeset ---
LiveMediaBuild: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
ProcEnviron:
 LANGUAGE=en_CA.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_CA.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)