First reset Ubuntu root Password: (Ensure you set a strong password)
sudo passwd root
Thereafter, install Openssh-Client
sudo apt update
sudo apt upgrade
sudo apt install openssh-client
To enable remote root Login via SSH, Open ssh config file
nano /etc/ssh/sshd_config
Then modify this line
PermitRootLogin yes
Finally, save and restart the SSH server
systemctl restart sshd
Ensuring that your hostname is set correctly
you can check using hostname or hostnamectl
To change hostname, you can do so by: