cat /etc/ssh/sshd_config | grep PermitRootLogin

PermitRootLogin no

cat /etc/ssh/sshd_config | grep Protocol

Protocol 2

cat /etc/ssh/sshd_config | grep Port

Port 56789

sudo iptables -A INPUT -p tcp -m tcp --dport 56789 -m comment --comment "SSH custom port" -j ACCEPT

ssh-keygen -t rsa -b 4096

eval $(ssh-agent -s)
ssh-add
ssh-add -l

4096 SHA256:gibberish /home/fictional_user/.ssh/id_rsa (RSA)
4096 SHA256:gibberish fictional_user@fictional_computer (RSA)

ssh-copy-id fictional_user@public_ip -p 56789

cat /etc/ssh/sshd_config | grep PasswordAuthentication

PasswordAuthentication no