I've been having the same problem, it started with a partial upgrade and now I have warnings:
apt warnings:
N: Missing Signed-By in the sources.list(5) entry for 'https://packages.zorinos.com/stable'
N: Missing Signed-By in the sources.list(5) entry for 'https://packages.zorinos.com/patches'
N: Missing Signed-By in the sources.list(5) entry for 'https://packages.zorinos.com/apps'
N: Missing Signed-By in the sources.list(5) entry for 'https://packages.zorinos.com/drivers'
N: Missing Signed-By in the sources.list(5) entry for 'https://packages.zorinos.com/premium'
zorin.sources file:
Types: deb
URIs: https://packages.zorinos.com/stable
Suites: noble
Components: main
Types: deb
URIs: https://packages.zorinos.com/patches
Suites: noble
Components: main
Types: deb
URIs: https://packages.zorinos.com/apps
Suites: noble
Components: main
Types: deb
URIs: https://packages.zorinos.com/drivers
Suites: noble
Components: main restricted
Types: deb
URIs: https://packages.zorinos.com/premium
Suites: noble
Components: main
Looking in the web found the following, but not sure will fix it:
Zorin OS users encountering the N: Missing Signed-By in the sources.list(5) entry for 'https://packages.zorinos.com/drivers' error can resolve it by editing the relevant sources file.
Navigate to the sources directory: cd /etc/apt/sources.list.d
Identify the file referencing the Zorin drivers repository (likely zorinos-ubuntu-drivers-noble.sources or similar).
Open the file with a text editor: sudo nano /etc/apt/sources.list.d/zorinos-ubuntu-drivers-noble.sources
Add the line Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg at the end of each entry block in the file.
Save and exit the editor.
Run sudo apt update to verify the error is resolved.
This fix ensures APT can verify package signatures using the system-wide Ubuntu archive keyring. If the issue persists, check for duplicate or conflicting entries in other .sources files and remove or comment them out.
But You have a zorin.list.save File, a zorin.sources and zorin.sources.save File and a zorin-list.distUpgrade File. Hmm ... I would have an Idea what we could try.
Open the Terminal and type:
cd /etc/apt/sources.list.d/
and press Enter. Then you should see the Path at the Beginning of the Line. Then type:
That should copy the 4 Files to Your Desktop. Please check that they are there before continuing. If Your Terminal is now still open, You don't need to do anything. If You should have closed it, open it again and type again cd /etc/apt/sources.list.d/
Then type sudo rm zorin.list.distUpgrade zorin.list.save zorin.sources zorin.sources.save to delete these Files there but do not delete the copied Files on the Desktop! These are the Backup! Then close the Terminal.
Then go to the Desktop, make a Right-Click and create a .txt File. Name it zorin.list and put it the following Content:
deb https://packages.zorinos.com/stable noble main
# deb-src https://packages.zorinos.com/stable noble main
deb https://packages.zorinos.com/patches noble main
# deb-src https://packages.zorinos.com/patches noble main
deb https://packages.zorinos.com/apps noble main
# deb-src https://packages.zorinos.com/apps noble main
deb https://packages.zorinos.com/drivers noble main restricted
# deb-src https://packages.zorinos.com/drivers noble main restricted
Save the File. Then open the Terminal again and type cd Desktop and then:
sudo cp zorin.list /etc/apt/sources.list.d/
And then make a sudo apt update && sudo apt upgrade
