How can I properly merge Debian DVDs into a single ISO for offline installation without prompts for extra discs?

I want to create a single bootable Debian ISO by merging **DVD1**, **DVD2**, and **DVD3** of Debian 10.13.0. My goal is to install Debian **offline**, using one ISO, and have access to all packages from all three DVDs **without being prompted to insert other discs** during installation. --- ### What I did: I'm on macOS. Here's my full procedure:

brew install p7zip xorriso dpkg

mkdir -p ~/Desktop/operation/combined/{dvd1,dvd2,dvd3,merged}
cd ~/Desktop/operation

7z x debian-10.13.0-amd64-DVD-1.iso -ocombined/dvd1
7z x debian-10.13.0-amd64-DVD-2.iso -ocombined/dvd2
7z x debian-10.13.0-amd64-DVD-3.iso -ocombined/dvd3

cp -a combined/dvd1/.             combined/merged/
cp -a combined/dvd2/pool/.        combined/merged/pool/
cp -a combined/dvd3/pool/.        combined/merged/pool/

cd combined/merged
mkdir -p dists/stable/main/binary-amd64
dpkg-scanpackages pool /dev/null > dists/stable/main/binary-amd64/Packages
gzip -k -f dists/stable/main/binary-amd64/Packages

cp -a ../dvd1/isolinux ./
cp -a ../dvd1/install ./
cp -a ../dvd1/.disk ./
cp -a ../dvd1/boot ./
cp -a ../dvd1/md5sum.txt ./

xorriso -as mkisofs \
  -r -J -joliet-long -iso-level 3 \
  -V "Debian Combined" \
  -o ~/Desktop/debian-combined.iso \
  -b isolinux/isolinux.bin \
  -c isolinux/boot.cat \
  -no-emul-boot -boot-load-size 4 -boot-info-table \
  -eltorito-alt-boot \
  -e boot/grub/efi.img \
  -no-emul-boot \
  .

### The problem: During installation, I still get prompted to insert other DVD, If I say "No", installation proceeds but only ~218 packages are installed (from DVD1). Packages from DVD2 and DVD3 are not used. ### Question : What am I missing to properly merge Debian DVDs into a single ISO that contains all packages and metadata, without the installer asking for additional DVDs?