As for pam_lastlog, add this to the PAM configuration for lightdm resolves the wtmp issue. The last command works again and all users logged in through lightdm are logged.
Due to the principal design of lightdm, there are no failed login attempts possible and therefore btmp is never written (this might be an issue to be addressed, since the current lightdm design allows an infinite number of unsuccessful logins!).
As for pam_lastlog, add this to the PAM configuration for lightdm resolves the wtmp issue. The last command works again and all users logged in through lightdm are logged.
Due to the principal design of lightdm, there are no failed login attempts possible and therefore btmp is never written (this might be an issue to be addressed, since the current lightdm design allows an infinite number of unsuccessful logins!).
Adrian