Issue: GDM fails to log in any users when authd is uninstalled

[adombeck]

Describe the issue

After uninstalling authd, selecting any user in the GDM login screen causes it to be stuck. The logs show:

Dec 17 16:50:45 ubuntu gdm-authd][12291]: PAM unable to dlopen(pam_authd.so): /usr/lib/security/pam_authd.so: cannot open shared object file: No such file or directory
Dec 17 16:50:45 ubuntu gdm-authd][12291]: PAM adding faulty module: pam_authd.so

Purging authd fixes the issue:

sudo apt purge authd

Steps to reproduce

1. Uninstall authd:

   sudo apt remove authd`
   

2. Try to log in via GDM with any user