SomeBoyoWhat are common practice's for hardening/securing your server?
Setup Fail2ban
Login only with SSH keys. MFA on SSH login. Use SSH proto 2.
Disable passwords, x11 forwarding, root logins
Reduce Idle timeout interval
Limit users’ SSH access
That should be more than enough for the average use case.
Possibly linuxContainers can help lock services down if you do it right.