[SOLVED] Missing Ubuntu 26.04.1 Default Sources after upgrade from 24.04.5

[DrexLock]

I upgraded my existing 24.04.5 install on my desktop to 26.04.1 without issue but noticed in Discover that the "Ubuntu 26.04.1 LTS" Sources section is not present, I included a screenshot because I wasn't exactly sure what the actual name of this section of sources is. I only noticed because the fresh install of 26.04.1 on my laptop does have it. I was able to view software sources on my desktop using software-properties-qt and flag the Chrome Repo to be included in updates. I did notice that the software-properties-qt window looks like it is an older version compared to what is on my laptop. Are there steps I can follow to fix Discover not showing the software sources menu and make sure it is as current as my laptop?

[Snowhog]

Asked Google AI:

why after upgrading from Kubuntu 24.04.5 to Kubuntu 26.04.1 is the Ubuntu 26.04.1 LTS Default Sources section missing in Discover

Response:


The Default Sources section is missing in KDE Discover because Ubuntu switched to the new deb822 .sources format stored in /etc/apt/sources.list.d/ubuntu.sources instead of the legacy /etc/apt/sources.list file, and Discover does not yet fully parse or display this modern format. [1, 2] Why This Happens

• Format Transition: Starting with Ubuntu 24.04 and continuing through later releases like 26.04, default package repositories are declared in modular deb822-style .sources files rather than the traditional one-line per file layout.
• Discover Limitation: KDE Discover's backend struggles to read or list repositories stored in these new paths, making the corresponding software sources interface vanish.
• System Functionality Unaffected: Your system packages still update normally via the terminal (apt update) because the APT package manager reads the new configuration correctly.

Asked Google AI:

online resource to rewrite Ubuntu .list sources files to the newer deb822-style .sources file format

Response:

While there is no prominent standalone web app or browser-based generator to copy-paste your lines online, there are official automated terminal commands and open-source GitHub scripts that perform this conversion natively.

The easiest and safest way to rewrite your Ubuntu .list files into the deb822 .sources format is to use the tools already built into your system or available on public repositories.

Method 1: The Native APT Command (Recommended)

If you are running Ubuntu 25.04 or newer, APT includes a built-in subcommand to automatically transition your files: [1]

sudo apt modernize-sources

• How it works: This command scans your legacy .list configurations, rewrites them into compliant .sources files inside /etc/apt/sources.list.d/, appends appropriate Signed-By security flags, and creates a backup of your old files (.list.bak). [2, 3]
• Note: If you are running an older release like Ubuntu 24.04 LTS, this command will throw an Invalid operation error because its version of APT does not have the subcommand yet. [1]

Method 2: Use an Online Open-Source Script

If you want to view a script's logic online or run an automated tool on an older Ubuntu version (like 22.04 or 24.04), you can utilize open-source scripts hosted on GitHub:

• ErikMichelson / apt-deb822-tool: This is a dedicated Bash parser that converts entries back and forth between "One-Line-Style" (.list) and "Deb822-style" (.sources). To convert an entire directory, you can run: [4, 5]
  apt-deb822-tool to-deb822 -W /etc/apt/sources.list.d
• Ubuntu Pro Client Script: Ubuntu natively maintains an internal python script for this layout. You can view its source code online or look for it locally on your machine at /usr/lib/ubuntu-advantage/convert_list_to_deb822.py. [6]

Method 3: Manual Mapping Reference

If you only have one or two repositories to move over, you can quickly write them by hand. The mapping translates single-line variables into a structured key-value template: [7, 8]

Legacy One-Line Format (.list):

New Deb822 Format (.sources):

If you'd like, I can help translate your configurations directly. Please share:

• The exact text of the .list files you want to convert
• Your current Ubuntu version (e.g., 24.04, 26.04)

[1] https://www.ssdnodes.com
[2] https://sleeplessbeastie.eu
[3] https://gist.github.com
[4] https://github.com
[5] https://unix.stackexchange.com
[6] https://askubuntu.com
[7] https://unix.stackexchange.com
[8] https://oneuptime.com


I would personally; and I think I may have used it myself; go with Method 1.

[Snowhog]

Asked Google AI:

why after upgrading from Kubuntu 24.04.5 to Kubuntu 26.04.1 is the Ubuntu 26.04.1 LTS Default Sources section missing in Discover

Response:


The Default Sources section is missing in KDE Discover because Ubuntu switched to the new deb822 .sources format stored in /etc/apt/sources.list.d/ubuntu.sources instead of the legacy /etc/apt/sources.list file, and Discover does not yet fully parse or display this modern format. [1, 2] Why This Happens

• Format Transition: Starting with Ubuntu 24.04 and continuing through later releases like 26.04, default package repositories are declared in modular deb822-style .sources files rather than the traditional one-line per file layout.
• Discover Limitation: KDE Discover's backend struggles to read or list repositories stored in these new paths, making the corresponding software sources interface vanish.
• System Functionality Unaffected: Your system packages still update normally via the terminal (apt update) because the APT package manager reads the new configuration correctly.

Asked Google AI:

online resource to rewrite Ubuntu .list sources files to the newer deb822-style .sources file format

Response:

While there is no prominent standalone web app or browser-based generator to copy-paste your lines online, there are official automated terminal commands and open-source GitHub scripts that perform this conversion natively.

The easiest and safest way to rewrite your Ubuntu .list files into the deb822 .sources format is to use the tools already built into your system or available on public repositories.

Method 1: The Native APT Command (Recommended)

If you are running Ubuntu 25.04 or newer, APT includes a built-in subcommand to automatically transition your files: [1]

sudo apt modernize-sources

• How it works: This command scans your legacy .list configurations, rewrites them into compliant .sources files inside /etc/apt/sources.list.d/, appends appropriate Signed-By security flags, and creates a backup of your old files (.list.bak). [2, 3]
• Note: If you are running an older release like Ubuntu 24.04 LTS, this command will throw an Invalid operation error because its version of APT does not have the subcommand yet. [1]

Method 2: Use an Online Open-Source Script

If you want to view a script's logic online or run an automated tool on an older Ubuntu version (like 22.04 or 24.04), you can utilize open-source scripts hosted on GitHub:

• ErikMichelson / apt-deb822-tool: This is a dedicated Bash parser that converts entries back and forth between "One-Line-Style" (.list) and "Deb822-style" (.sources). To convert an entire directory, you can run: [4, 5]
  apt-deb822-tool to-deb822 -W /etc/apt/sources.list.d
• Ubuntu Pro Client Script: Ubuntu natively maintains an internal python script for this layout. You can view its source code online or look for it locally on your machine at /usr/lib/ubuntu-advantage/convert_list_to_deb822.py. [6]

Method 3: Manual Mapping Reference

If you only have one or two repositories to move over, you can quickly write them by hand. The mapping translates single-line variables into a structured key-value template: [7, 8]

Legacy One-Line Format (.list):

New Deb822 Format (.sources):

If you'd like, I can help translate your configurations directly. Please share:

• The exact text of the .list files you want to convert
• Your current Ubuntu version (e.g., 24.04, 26.04)

[1] https://www.ssdnodes.com
[2] https://sleeplessbeastie.eu
[3] https://gist.github.com
[4] https://github.com
[5] https://unix.stackexchange.com
[6] https://askubuntu.com
[7] https://unix.stackexchange.com
[8] https://oneuptime.com


I would personally; and I think I may have used it myself; go with Method 1.

[DrexLock]

Thanks for the assist Snowhog, I ran sudo apt modernize-sources and confirmed that all sources are modern. But even after a reboot Discover is still not showing Default Sources. This install was originally 17.10 that I've been in-place upgrading from LTS to LTS since 18.04, could that be compounding the issues created with issues created in the transition to deb822-style with Packagekit and Discover?

[Snowhog]

Discover should be reading the new .sources files without issue; it does here on my Kubuntu 26.04 PCs. Have you ensured that Discover has finished fetching all updates? On my laptop, it is taking a considerable amount of time to do so, and until it does, this section won't be shown. On my Desktop PC (a MUCH faster rig), this isn't an issue.

[DrexLock]

You were right! I had left Discover up in the background and checked it again and Ubuntu 26.04.1 LTS Default Sources are showing now. I must have just not given it enough time after I checked for it to sort itself. Thanks again for the help Snowhog!