Modify

/etc/apt/sources.list

with a text editor as root (superuser). The example below uses gedit, but you may use nano or another text editor of your choice.

• Become superuser:

  su

• Make a backup copy:

  cp /etc/apt/sources.list /etc/apt/sources.list.YYYYMMDD

• Open sources.list for modification:

  gedit /etc/apt/sources.list

• Add the appropriate lines to connect to the local server:

  deb [trusted=yes] http://192.168.0.101/debian12/Deb-64bit-disc_1/ bookworm main
  deb [trusted=yes] http://192.168.0.101/debian12/Deb-64bit-disc_2/ bookworm main
  deb [trusted=yes] http://192.168.0.101/debian12/Deb-64bit-disc_3/ bookworm main
  ...
  deb [trusted=yes] http://192.168.0.101/debian12/Deb-64bit-disc_21/ bookworm main

• Save the modified document.

Use one of the following methods:

• Open Synaptic Package Manager.
• Click Reload to update the list of available packages.

• As superuser:

  apt update

Now you can install or uninstall packages as needed.