So the default behavior of the Ubuntu login screen was that it would match match my Desktop wallpaper. So for example, if I was on the login screen and I clicked between my username and the Guest user, the wallpaper would change to either the same wallpaper that was on my Desktop, or the "default" wallpaper for guest.
In an attempt to disable the Guest user, I ran this command:
echo allow-guest=false | sudo tee -a /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf
However, now that I've done this, the Ubuntu login screen no longer matches the wallpaper that's on my Desktop, it's just stuck on the default one.
I tried going back to this file and removing the "allow-guest=false" line altogether, but this hasn't changed anything. The Guest account is re-enabled, but the wallpaper on the login screen still isn't matching my Desktop wallpaper.
I've found many posts on how to make the Login and Desktop wallpapers different, but I want it to go back to the default behavior where the Login wallpaper matches my Desktop wallpaper. I can't seem to find any posts on this. Is there a conf file somewhere that may have gotten messed up? I'm tempted to just reinstall Ubuntu but surely there's a much simpler fix...
I just wiped and reinstalled Ubuntu, and remounted /home (/home is kept on a separate partition), and now a slightly different version of the issue is happening. If I use one of the built-in Ubuntu wallpapers, everything works as it's supposed to. However, if I use a wallpaper from ~/Pictures, then the issue resurfaces. The login screen changes back to the ugly default one. I feel like there's gotta be a setting or config file somewhere that's causing the problem. Could it be something in /home?
Someone on reddit suggested changing the wallpaper from Firefox. This works, if I change the background from Firefox then both the Desktop and Login wallpapers match like they're supposed to. So that means it's gotta be some sort of permissions and/or groups related thing at this point, right?
Also just noticed that this created a file in /home called Firefox_wallpaper.png, so if LightDM has access to that, maybe the problem isn't my /home folder, but with my ~/Pictures or ~/Pictures/Wallpapers folders... hmm...