SSH & Git Options
Two small choices in the Options step: whether to run an SSH server, and what git should call you.
Both live in the Options step, next to the rescue media toggle.
SSH server
Enable SSH is off by default. Turning it on installs openssh, enables sshd with a drop-in configuration that disables root login over SSH, and opens a firewall exception for port 22. With it off, sshd is explicitly disabled. Root login itself is locked either way. All of this is applied at first boot, once the network is up, and the policy is described in Security.
Git identity and SSH key
Enter a name and an email to have them set as your global user.name and user.email. Both must be given, or both left blank to skip; the email is checked for a plausible shape.
Whatever you choose, first boot also generates an ed25519 SSH key for your account at ~/.ssh/id_ed25519 if you do not already have one, with no passphrase. Add the public key, ~/.ssh/id_ed25519.pub, to your git host. Only SSH is set up: there is no HTTPS credential helper. The key is created once; an existing key is never replaced.
The same fields exist in an unattended answer file as ssh_enabled, git_name, and git_email.