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
To save you troubles with discovery issues, i prefer installing SAMBA server,