I have a user without a password set (i.e.
I would not like to use public keys on this setup.
Is there a way to SSH login to such a user?
PermitEmptyPasswords yes then restart sshd ?
If you just want to become the user in question, the simplest way is to log in as some other user (via ssh) and
su $username. This requires root privilegies, but you could put the command in
/etc/sudoers and only let your user execute that command as root.
If you really want to login through ssh (or remotely in some other way), you need to pick one of the following:
sshd_config and restart