This one is similar to persistent local SSH server forwarding setup (although much more simple). Preparation part is exactly the same, so if you've already done that, you may skip it and go straight to persistent SSH proxy configuration.

After each file and command there will be a location label …

SSH keys come in pairs: a public and a private key. It might be easier to think of them as a lock (public part) and key (private part). You add public key (lock) to the computer you want to connect to, and then you can connect from elswhere and unlock …

(
  username=support
  icon_path=/var/lib/AccountsService/icons/$username

  sudo adduser --gecos '' $username
  sudo adduser $username sudo

  sudo wget -qO "$icon_path" https://shevchuk.co/cog.png
  echo "[User]" | sudo tee /var/lib/AccountsService/users/$username
  echo "Icon=$icon_path" | sudo tee -a /var/lib/AccountsService/users/$username
)

Hide user …