You may want to update this post to disable password authentication, and thus you'll no longer need to install fail2ban. An important goal is to tighten your attack surface, not expand it. At this point you will still have an exposed SSHd server, so I'd recommend throwing the server under tailscale. You can setup the SSHd listener to use your tailscale IP or setup tailscale for SSH via ACLs (https://tailscale.com/tailscale-ssh).

Additionally you can further tighten controls of incoming logins with the use of AllowGroups to tighten your controls on which groups can log into the system. This would mitigate a scenario where an adversary is able to escalate enough privileges to write an .authorized_keys file to a non-privileged user which may have a shell still configured.

Finally, unless you're treating this server as a bastion host of sorts, you probably should disable forwarding for agents or X11 etc. We've seen a lot of adversaries move laterally due to this agent forwarding.