trying to install Ubuntu Studio but couldn't finish due to lack of GRUB bootloader?
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.2
ProcVersionSignature: Ubuntu 5.4.0-42.46-lowlatency 5.4.44
Uname: Linux 5.4.0-42-lowlatency x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckMismatches: ./boot/grub/efi.img
CasperMD5CheckResult: fail
CasperVersion: 1.445.1
Date: Fri Sep 18 16:48:04 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntustudio.seed quiet splash ---
LiveMediaBuild: Ubuntu-Studio 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)
It appears this failed because your live system had previously managed to download apt sources for the -updates pocket, but at the time of installing the bootloader (which has a newer version in -updates), the network was no longer available.