For Smallstep SSH clients

Depending on your install method, uninstall the step CLI, usually through a package manager uninstall.

Delete your step config directory at ~/.step.

Remove the lines that look like this from your ~/.ssh/config:

Host *
    Include "/Users/yourname/.step/ssh/config"

For Smallstep SSH hosts

Edit /ets/ssh/sshd_config and remove autogenerated SSH config lines like this:

# autogenerated by step @ 2021-04-02T19:17:47Z
TrustedUserCAKeys /etc/ssh/ca.pub
HostCertificate /etc/ssh/ssh_host_ed25519_key-cert.pub
HostKey /etc/ssh/ssh_host_ed25519_key
# end

Delete /etc/ssh/ca.pub and /etc/ssh/ssh_host_ed25519_key-cert.pub. The filename of the latter may differ depending on the type of key used.

Delete the step config directory at /root/.step.

Deactivate Smallstep SSH:

step-ssh deactivate

Lastly, remove the step-ssh package.