Trying to use this theme makes nody-greeter unusable (Pop OS 20.04 LTS)

[MariaGratiaPlena]

If I use the default theme (gruvbox) all the sessions start correctly; However, if I try to use this theme or the simple theme, the error

"LightDM couldn't start session
The provided session: "ubuntu" couldn't be started
Session returned error code 1"

shows up.
Then, if I try to load the default theme using the button provided in the error, it becomes unable to start up any session.

This is how my /etc/lightdm/lightdm.conf looks like:

[SeatDefaults]
user-session=xfce
greeter-session=nody-greeter

But the error message doesn't change even if I try to change the user-session value to the .desktop file name of the other ones I have installed. What should I do?

[mshernandez5]

I just created a VM with Pop OS 22.04 LTS (20.04 LTS no longer available) to test the theme and was able to get it working.

Change /etc/lightdm/lightdm.conf to the following:

[SeatDefaults]
user-session=pop
greeter-session=nody-greeter

Restart and try to login again, that should be the right session for Pop OS.

Also make sure you don't have any other configurations with conflicting values under the /etc/lightdm/lightdm.conf.d/ folder, any configuration files there will be applied as well.

Let me know if that solves your issue.

[MariaGratiaPlena]

[SeatDefaults]
user-session=pop
greeter-session=nody-greeter

Restart and try to login again, that should be the right session for Pop OS.

I changed the title of the issue and I forgot to specify that I usually use xfce as my default session, but I already tried to change it to pop and it gives me the same error. Also, the /etc/lightdm/lightdm.conf.d/ folder seems to be empty.
Maybe is the Pop OS version to cause this error in some way? I'll try to update it and see what happens. It seems kinda a stretch, but I see no harm in giving it a try.

[mshernandez5]

Maybe is the Pop OS version to cause this error in some way? I'll try to update it and see what happens. It seems kinda a stretch, but I see no harm in giving it a try.

No need to try updating the version. I don't think the version made any big difference but wanted to point out that the test I did was not exactly the same.

I usually use xfce as my default session

Ooh ok, that makes sense, then I would assume user-session=xfce would probably be correct then.
Since neither pop nor xfce work and you're getting a message that says "ubuntu" couldn't be started it seems like it's ignoring the setting there entirely.

Just to make sure, I changed my /etc/lightdm/lightdm.conf to user-session=test (which doesn't exist) then I did get a "test" couldn't be started message on login. For some reason, something is setting ubuntu as the default greeter session and I am not sure what that might be, but I'll think about it.

The reason why you see this problem on only this theme and the simple theme is because these themes select the session different than most. Most themes will ask the greeter for a list of all available sessions, let the user choose from that list in the interface, then on login will pass the name of the session selected by the user. The simple theme and WelcomeXP instead just asks the greeter what the default session is set to and will always ask for that session on login, whether it actually exists or not. For some reason the greeter is telling these themes that the default session is ubuntu.

[mshernandez5]

When you get a chance, run lightdm --show-config and see what is listed for user-session under the [Seat:*] section.
If it shows ubuntu then check every file in the sources section to see where that is being set.

Interesting thing I also noticed is that if you don't specify a user-session in the configuration at all, it defaults to ubuntu for me, so definitely make sure it shows up in the list:

$ lightdm --show-config
   [Seat:*]
A  allow-guest=false
G  greeter-wrapper=/etc/lightdm/Xgreeter
D  guest-wrapper=/usr/lib/lightdm/lightdm-guest-session
H  greeter-session=nody-greeter
F  xserver-command=X -core
H  user-session=pop

[MariaGratiaPlena]

No need to try updating the version. I don't think the version made any big difference but wanted to point out that the test I did was not exactly the same.

I actually decided to update to 22.04 LTS and it now works fine without changing the lightdm.conf or any configuration file... So I guess it actually makes a difference.

Also, while I was using the old version I also tried like you did to change the user-session value to something without sense like "test" and it just kept ignoring it.

[mshernandez5]

Glad it works now but that is strange, sometime I'll have to find a copy of 20.04 LTS and see if there is issues on a clean installation. If there is I might have to put a note in the README.

[furretgd1]

I'm continuing the issue here, I'm using Arch Linux opposed from using a distribution that pre-includes LightDM I did the installation and setup manually. So this could be a setup/configuration issue. I'm unfamiliar with the purpose of .session files but in Arch Linux they aren't there because I presume it relies on the .desktop files for entries for LightDM. When trying to login via WelcomeXP it complains that the default session doesn't exist so same issue which was listed above hence why I'm putting the issue here and to try with the alternative Nody Greeter default theme. Which successfully manages to get somewhere as I am greeted with a black screen with a moving cursor rather than failing to even find the xfce session. But it isn't able to get past that. For sanity sake I installed the GTK theme for lightdm lightdm-gtk-greeter which successfully works. The only difference is I'm not git checking out. Since I'm using the latest versions of Nody-Greeter and WelcomeXP. I'm also using NodeJS 18 not 16 since it's not in the Arch Repos anymore but I was successful in building and installing Nody-Greeter with NodeJS 18. So I'm not exactly sure what's causing this issue. If you have better knowledge about LightDM maybe any configuration steps I might of missed and should consider let me know.

My user session has been set to xfce and I've also left it commented out but both produced the same result. My best guess myself is I could be missing session files. But it's unclear what's put inside of them. As for Nody-Greeter not working at all with the other theme. I might need to investigate that as well but if you can provide help as to why it might be struggling to get into the XFCE desktop with the default nody-greeter theme let me know too! I appreciate you taking the time to read this