I had forgotten about rlogin. How are you actually using it? rlogin on debian/ubuntu is a symlink to ssh by default nowadays.
aaron@omv5dev:~$ ls -al /usr/bin/rlogin
lrwxrwxrwx 1 root root 24 Jan 13 2020 /usr/bin/rlogin -> /etc/alternatives/rlogin
aaron@omv5dev:~$ ls -al /etc/alternatives/rlogin
lrwxrwxrwx 1 root root 15 Jan 13 2020 /etc/alternatives/rlogin -> /usr/bin/slogin
aaron@omv5dev:~$ ls -al /usr/bin/slogin
lrwxrwxrwx 1 root root 3 Jan 31 2020 /usr/bin/slogin -> ssh
You still have to have port 22 open. To use it: rlogin username@IP address of the computer you want to connect, You need to have an account on that computer, of course. I use "rlogin" because that is what I had been using for a long, long time in UNIX. Syntax is the same as ssh.