At least Kubuntu can use our ‘
univention-domain-join’ if you choose to use it within a terminal. KDE uses a login manager that is currently not recognized but doesn’t need any configuration - it recognizes a domain setup and handles the login accordingly. So it is safe to just skip this step and configure the system to authenticate against a DC.
user@kubuntu:~$ sudo univention-domain-join-cli --skip-login-manager
You might try this with similar distros too but surely it won’t work with distros that use different methods to configure domain authentication.