Ubuntu has a set of scripts you can run to harden a new server (not advisable on a server that has already been configured for something). You need an Ubuntu Pro subscription to access them but you can get a free trial and then cancel it after you've finished.
I did this process for a customer recently and it was pretty straightforward and much much more thorough (over 100 configuration changes) than just tweaking SSH and fail2ban.
I expect other commercially-oriented distros offer something similar.