Can't sign in to COSMIC desktop if password contains the letters "ä", "å" or "ö"

[RPGRoger]

Distribution:
NAME="Pop!_OS"
VERSION="24.04 LTS"
ID=pop
ID_LIKE="ubuntu debian"
PRETTY_NAME="Pop!_OS 24.04 LTS"
VERSION_ID="24.04"
HOME_URL="https://pop.system76.com"
SUPPORT_URL="https://support.system76.com"
BUG_REPORT_URL="https://github.com/pop-os/pop/issues"
PRIVACY_POLICY_URL="https://system76.com/privacy"
VERSION_CODENAME=noble
UBUNTU_CODENAME=noble
LOGO=distributor-logo-pop-os

Issue/Bug Description:
Can't sign in to COSMIC desktop because I chose a password with the letters "ä", "å" or "ö".
Get error message "path_authenticate: AUTH_ERR" when trying to sign in with the password I set during installation.

Steps to reproduce:
Install Pop!_OS 24.04 alpha on an Lenovo ideapad 320 via USB flash drive and Ventoy. During installation, choose Swedish ("Svenska") as default language (and Swedish "Default" keyboard layout). I chose not to encrypt the drive (if it makes any difference). Name and username contained latin-based letters (that is, no "å", "ä", or "ö"). There's no error showing during installation. The error occurs after reboot and at the login screen.

Other Notes:
I re-installed the distro several times to locate the bug. The error does not occur if you make a password with Latin-based letters, even if you choose Swedish as default language/keyboard layout during installation.

[KerrLeada]

I have had this issue as well (I was about to create an issue about it), and not just "å", "ä", "ö". Special letters like "+" also has the same issue.

It's not just affecting the password set during the installation. I tested adding a user with the "adduser" tool and if I gave it a password containing e.g. "+" then I wouldn't be able to login. The user was created and the password was accepted during creation, but the login screen didn't allow me to login. It just gave me the same "path_authenticate: AUTH_ERR" error as mentioned by the issue if I tried (at least I think that was the error, it was something like that).

[Wasabi375]

I have a similar issue during login using a german keyboard layout. On the german keyboard layout the z and y keys are swapped. When trying to log in with a password containing the letter y I have to type z instead.
This only happens when logging in. When I have to type my password after I lock the screen the x and y keys are no longer swapped.

This might be related to lilyinstarlight/nixos-cosmic#332
TL;DR: xkb-data has some paths hard coded in version 0.1. This is fixed in version 0.2.1. cosmic-greeter is still using version 0.1.
I tried install a patched version locally, but failed miserably. I guess I am a bit new to nixos and linux development and I don't have the time right now to figure out how to do this. I might have some time next weekend to test this idea properly.

[Wasabi375]

This is fixed for me at least. I'm on alpha 4 right now.