There are no APT sources configured in /etc/apt/sources.list or /etc/apt/sources.list.d.

[ Impact ]

 * 24.04 changed apt sources to deb822 format. This causes landscape-client's
   package-reporter to report errors to landscape-server, specifically "There
   are no APT sources configured in /etc/apt/sources.list or
   /etc/apt/sources.list.d". This error doesn't block package reporting, but it
   does impact reporting of configured APT sources.

 * This affects all releases with deb822 sources - noble onward - and so should
   be applied to noble

 * The patch turns on deb822 support only if it is available to preserve
   backward compat

[ Test Plan ]

 * Reproducing the bug should requires registering a client with a Landscape
   Server

sudo apt install landscape-client
sudo landscape-config # progress through the wizard

 * After some time, server should report "1 computer is having issues reporting
   packages" in the alerts panel in the top right.

 * Navigating to /account/<account_name>/computers/?criteria=alert:package-reporter
   lists the registered computer.

 * Clicking the alert in the alerts panel shows the registered computer in the
   list, along with Error output "There are no APT sources configured in
   /etc/apt/sources.list or /etc/apt/sources.list.d."

[ Where problems could occur ]

 * Reporting on non-deb822 *.list sources could break, alone or when present in
   combination with deb822 sources.

 * Landscape package activities: install, remove, upgrade could fail or could
   fail to report packages after they complete.

 * This is a change to landscape/lib, which is also used in landscape-sysinfo,
   part of motd. If it breaks, it could cause issues in the login MOTD.

[ Other Info ]

 * Landscape server can still instruct the client to write non-deb822 sources,
   this fix only targets reporting of deb822 sources, not configuration of
   sources.

=== ORIGINAL BUG REPORT FOLLOWS ===

It looks like 24.04 is changing how apt sources work..

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=23.10
DISTRIB_CODENAME=mantic
DISTRIB_DESCRIPTION="Ubuntu 23.10"
$ cat /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu mantic restricted main multiverse universe
# deb-src http://archive.ubuntu.com/ubuntu mantic restricted main multiverse universe
deb http://archive.ubuntu.com/ubuntu mantic-updates restricted main multiverse universe
# deb-src http://archive.ubuntu.com/ubuntu mantic-updates restricted main multiverse universe
deb http://archive.ubuntu.com/ubuntu mantic-security restricted main multiverse universe
# deb-src http://archive.ubuntu.com/ubuntu mantic-security restricted main multiverse universe
deb http://archive.ubuntu.com/ubuntu mantic-backports restricted main multiverse universe
# deb-src http://archive.ubuntu.com/ubuntu mantic-backports restricted main multiverse universe

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=24.04
DISTRIB_CODENAME=noble
DISTRIB_DESCRIPTION="Ubuntu Noble Numbat (development branch)"
$ cat /etc/apt/sources.list
# Ubuntu sources have moved to /etc/apt/sources.list.d/ubuntu.sources
$ cat /etc/apt/sources.list.d/ubuntu.sources
Types: deb
URIs: http://archive.ubuntu.com/ubuntu/
Suites: noble noble-updates noble-backports
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

Types: deb
URIs: http://archive.ubuntu.com/ubuntu/
Suites: noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

With this, Landscape is now reporting an alert "Package reporting issues":

There are no APT sources configured in /etc/apt/sources.list or /etc/apt/sources.list.d.