I take back everything I said about fail2ban on debian - it’s a broken pile of crap - won’t run with the debian defaults…
I really can’t be arsed figuring it out either…
I’ve just disabled the NAT rule on my router… I just re-hooked up my Pi4 after I noticed in Feb the fan and heatsink on it were f–ked (was running as high as 85 c) - now idling on around 45-50c)… So I have a NAT rule to let me SSH to the Pi4 too - and that is running Ubuntu …
OK - figured it out - fail2ban is different beast than I remember it being on Debian Stretch…
I fixed it on Debian Bookworm (Raspberry Pi 5) by running
fail2ban-client start
Then restarting fail2ban in systemd…
Never had to use/run fail2ban-client before… pezzo-di-merda!