Comment 4 for bug 2033900

After reboot I can't do update+upgrade, sources.list is broken:
corrado@corrado-n16-mm-0901:~$ sudo apt update && sudo apt upgrade
[sudo] password for corrado:
Get:1 file:/cdrom mantic InRelease
Ign:1 file:/cdrom mantic InRelease
Get:2 file:/cdrom mantic Release
Err:2 file:/cdrom mantic Release
  File not found - /cdrom/dists/mantic/Release (2: No such file or directory)
Hit:3 http://it.archive.ubuntu.com/ubuntu mantic InRelease
Hit:4 http://it.archive.ubuntu.com/ubuntu mantic-updates InRelease
Hit:5 http://it.archive.ubuntu.com/ubuntu mantic-backports InRelease
Hit:6 http://it.archive.ubuntu.com/ubuntu mantic-security InRelease
Reading package lists... Done
E: The repository 'file:/cdrom mantic Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
corrado@corrado-n16-mm-0901:~$ cat /etc/apt/sources.list
deb [check-date=no] file:///cdrom mantic main restricted
corrado@corrado-n16-mm-0901:~$ cat /etc/apt/sources.list.d/original.list
# Ubuntu sources have moved to /etc/apt/sources.list.d/ubuntu.sources
corrado@corrado-n16-mm-0901:~$ cat /etc/apt/sources.list.d/ubuntu.sources
Types: deb
URIs: http://it.archive.ubuntu.com/ubuntu
Suites: mantic mantic-updates mantic-backports
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

Types: deb
URIs: http://it.archive.ubuntu.com/ubuntu
Suites: mantic-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
corrado@corrado-n16-mm-0901:~$ cat /var/log/installer/media-info
corrado@corrado-n16-mm-0901:~$

Will keep this system for future test if needed. Now I'm writing from a Mantic installed in a different partition from the ISO dated 0929.