Everything was ready out the box...

I did have fun as my configuration in my client application was set to point to an IP rather than the hostname.

Some related notes:
  * SFTP: https://linuxconfig.org/how-to-setup-sftp-server-on-ubuntu-20-04-focal-fossa-linux
  * https://www.howtogeek.com/50787/add-a-user-to-a-group-or-second-group-on-linux/
  * https://www.digitalocean.com/community/tutorials/how-to-use-sftp-to-securely-transfer-files-with-a-remote-server
  * https://wordpress.org/support/topic/the-session-allows-sftp-connections-only/

Note, I'd added the user account to the group "sftp" which then made it specifically an ''sftp'' account and blocked it for ''ssh'' using the basic configuration. I got the error "the session allows sftp connections only" when trying to ''ssh''. Removing the account from the group fixed things.

<code bash>
# Create sftp group and add user
groupadd sftp
usermod -a -G sftp david

# Restart SSH - 2 methods
systemctl restart ssh
service ssh reload

# Remove user from group
gpasswd -d david sftp

# View groups
groups david
</code>

====== Disable Passwords ======

Make sure you have a key (or a host who can let you back in if you loose it) before doing this.

Edit the file:
<code bash>
sudo vi /etc/ssh/sshd_config
</code>
Change this bit from "yes" to "no":
<code>
# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication no
#PermitEmptyPasswords no
</code>
Restart SSH:
<code bash>
sudo systemctl restart ssh
</code>