Are you familiar with port knocking? My servers will only open port 22, or some other port, after two specific ports have been knocked on in order. It completely eliminates the log files getting clogged.
The bots have been port scanning me for decades. They just don't know which two ports to hit to open 22 for their IP address. Simply iterating won't get then there, and fail2ban doesn't afford them much opportunity to probe.
Did you really notice a significant drop off in connection attempts? I tried this some years ago and after a few hours on a random very high port number I was already seeing connections.
I use a non standard port and have not had an unknown IP hit it in over 25 years. It's not a security feature for me, I use that to avoid noise.
My public SFTP servers are still on port 22 and but block a lot of SSH bots by giving them a long "versionaddendum" /etc/ssh/sshd_config as most of them choke on it. Mine is 720 characters long. Older SSH clients also choke on this so test it first if going this route. Some botters will go out of their way to block me instead so their bots don't hang. One will still see the bots in their logs, but there will be far less messages and far fewer attempts to log in as they will be broken, sticky and confused. Be sure to add offensive words in versionaddendum for the sites that log SSH banners and display them on their web pages like shodan.io.
In my experience can cut out the vast majority of ssh connection attempts by just blocking a couple IPs. ... particularly if you've already disabled password auth because some of the smarter bots notice that and stop trying.
