Fresh install Ubuntu 20.04 LTS from USB Session non-EFI

Again APT configure crash from CD but this time, i had unchecked CD-Rom source in software and update screen before beginning install

I think the answer is in the script installing Obuntu, so how to change this script ?

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: ./dists/focal/main/binary-i386/Release ./dists/focal/main/binary-i386/Packages.gz ./pool/main/e/efibootmgr/efibootmgr_17-1_amd64.deb ./pool/main/e/expat/libexpat1_2.2.9-1build1_i386.deb ./pool/main/libx/libxdamage/libxdamage1_1.1.5-2_i386.deb ./pool/main/n/nvidia-prime/nvidia-prime_0.8.14_all.deb ./pool/main/l/lupin/lupin-support_0.57build1_amd64.deb ./pool/main/l/llvm-toolchain-9/libllvm9_9.0.1-12_i386.deb ./pool/main/m/mesa/mesa-vdpau-drivers_20.0.8-0ubuntu1~20.04.1_amd64.deb ./pool/main/m/mesa/libgl1-mesa-dri_20.0.8-0ubuntu1~20.04.1_i386.deb
CasperMD5CheckResult: skip
CasperVersion: 1.445.1
Date: Fri Oct 23 01:11:01 2020
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed initrd=/casper/initrd quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)