Hello.
Thanks for reading that topic.
In Lubuntu 20.04 is possible change the SDDM login screen background editing
/usr/share/sddm/themes/lubuntu/theme.conf
[General]
background=path/filename.png
Doing that same action in 24.04 not works.
In next startup SDDM background will be totally blank.
How change the SDDM login background image in 24.04 ?
Have an nice night.
To change the SDDM background in Lubuntu 24.04 Noble:
Open the SDDM configuration file using a text editor like nano, vim, or gedit.
The file is typically located at /usr/share/sddm/themes/breeze/theme.conf.
sudoedit /usr/share/sddm/themes/breeze/theme.conf
Locate the line that sets the background image. It will look similar to this:
background=/usr/share/wallpapers/Kay/contents/images_dark/5120x2880.png
Replace the path to the current image with the path to the new image.
For example, if you want to use an image located at /usr/share/wallpapers/my-wallpaper.png, change the line to:
background=/usr/share/wallpapers/my-wallpaper.png
Save the file and restart the SDDM service to apply the new background image.
You can restart the SDDM service using the following command:
sudo systemctl restart sddm
Alternatively, you can use the SDDM configuration settings in the Lubuntu system settings to change the theme and background image. Navigate to the SDDM settings and choose a different theme or customize the current theme to set a new background image.
Remember to ensure that the new background image is accessible and correctly referenced in the configuration file. If you encounter issues, check the file permissions and paths carefully.
I hope all this helps. 
@aug7744
To have the same login screen as in Lubuntu 20.04 you can indeed proceed as you have written but additionally you have to set the ‘lubuntu’ theme in SDDM Configuration:
Applications Menu → Accessories → SDDM Configuration → Theme → choose ‘lubuntu’ as current theme name from the menu → Save
[Addendum: See post #6]
@1fallen
I fear as default there is no folder /usr/share/sddm/themes/breeze/ in Lubuntu 24.04. Aside this you have described the same procedure as aug7744 has done, doesn’t you?
The clock on the default login screen is a nice feature. But to have it, no theme at all has to be chosen in SDDM Configuration. Hence, there seems to be no theme.conf file one can edit. Perhaps that’s the point of the entry post of aug7744. If not, may I ask whether it’s possible to choose an individual background image for the login screen together with the clock?
I’m pretty sure I had it early in development, or perhaps I manually installed the breeze theme.
Lubuntu is a good system it’s just not for me is all.
I think we need @wxl to help on this.
Place your chosen-background picture in /usr/share/sddm/themes/lubuntu
Then, you have to edit the following file
sudo nano /usr/share/sddm/themes/lubuntu/theme.conf
[General]
background=chosen-background
Save and exit
I’ve just verified it in VirtualBox: @tea-for-one has done it. The background picture has to be placed into the folder /usr/share/sddm/themes/lubuntu.
No edit of SDDM Configuration as described in my post above is necessary.
The wallpaper file can be in any folder.
You just have to give it the correct path.
OP probably just misspelled it e.g (‘.png’ instead of ‘.jpg’ ?).
If you get a white blank, it means it couldn’t load the picture.
journalctl -b | grep Background.qml
might give you a clue.
Exactly as I said LOL:
cat /usr/share/sddm/themes/lubuntu/theme.conf
[General]
background=/home/me/Downloads/breno-machado-in9-n0JwgZ0-unsplash.png
That location won’t work. See post #10 and #9
inxi -F
System:
Host: me-standardpc Kernel: 6.11.0-24-generic arch: x86_64
bits: 64
Desktop: LXQt v: 1.4.0 Distro: Lubuntu 24.04.2 LTS (Noble
Numbat)
I had to check I wasn’t losing my mind…
I don’t think that this is correct.
For example, if the chosen background is in the user’s home directory, the log in screen will not be able to display it because the user’s home directory is not mounted until after log in.
I agree with @tea-for-one…mine I placed directly into the same directory as the theme.config is located ‘/usr/share/sddm/themes/ubuntu-theme’
But changed the line:
cat /usr/share/sddm/themes/lubuntu/theme.conf
[General]
background=breno-machado-in9-n0JwgZ0-unsplash.png
Tested on Lubuntu 25.04 and it works nicely. No need for any other fiddling.
Also works nicely 
Thanks for all replies.
@tea-for-one had replied the solution.
In 20.04 SDDM use the image if is in /home/username , but anything was changed not being possible to do it in 24.04.
In 24.04 the image file need is in /usr/share/sddm/themes/lubuntu/ or in other mounted partition not being /home.
Now the image load correctly in SDDM.
Have a nice week.
Please mark the post from @tea-for-one as the solution to close this topic.
This not only gives credit to the user who helped you but also makes it easier for others to find the solution if facing the same/similar issue.
Thanks.
@rubi1200
Thanks for saying it.
Have an nice week.
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