Joining linux servers to Microsoft AD for user login and authentication can be a daunting task. The following is the simplest (in my opinion) way to join an Ubuntu server or workstation to AD. This method was tested on Ubuntu 18.04 LTS and allows the use of AD group for SSH access and file permissions. It also automatically creates the local home directory when a user logs in.
Enable the universe repository (required for krb5-user package):