We start by creating a new user and authorizing SSH-based access for an SSH key pair.
sudo adduser fideloper
# Locally:
# cd ~/.ssh
# ssh-keygen -o -a 100 -t ed25519 -f id_ed
# cat id_ed.pub | pbcopy
# Back on server when logged in as user "fideloper":
echo "your-public-key" >> ~/.ssh/authorized_keys