I use LDAP for user authentication.
If the password on the server has expired, when I login with ssh I get these
prompts:

Password:
Password expired. Change your password now.
Current Password:
New password:
Retype new password:

sddm doesn't know how to handle such situation. After I type the username and
password it freeze. No login happens, no message is shown, it is not possible
to login any more even with an account with valid password.

kdm instead has not trouble to handle an account with expired password.