When updating OCP 4.12.25 to OCP 4.13.6 with a ssshd_config modified, ssh logins are no longer possible.
With OCP 4.13 we introduced ssh-key-dir which is reading ssh user keys from /var/home/core/.ssh/authorized_keys.d and would require sshd_config is added `Include /etc/ssh/ssh_config.d/*.conf`. This works if sshd_config is not altered, however if it is, it is not touched by the upgrade process and ssh login is no longer possible

OCP 4.13.6 updated from 4.12.25 with changed sshd_config

install OCP 4.12.25 , change sshd_config (allow password login), set password for core user, upgrade to 4.13.6

1. Install OCP 4.12.25 disconnected 

2. set core user password
   $ ssh -t sno "echo core:<password> |sudo  /sbin/chpasswd"

3. change sshd_config to allow password login and validate and restart sshd
   $ ssh -t sno "sudo /bin/sed 's/PasswordAuthentication no/PasswordAuthentication yes/' -i /etc/ssh/sshd_config"
   $ ssh -t sno sudo grep PasswordAuthentication /etc/ssh/sshd_config
   $ ssh -t sno sudo systemctl restart sshd

4. validate login via password (from a node not having the key

5. upgrade to OCP 4.13.6

6. try to login to system as user core  via password or w/ key --> failing

7. use oc node debug node/<nodename> ,check sshd_config and find `Include /etc/ssh/ssh_config.d/*.conf`.  is missing

login via ssh no longer possible

ssh login possible 

none