Linux Shout shows you how to install Fail2ban on Debian 10 or 11.
How to install Fail2ban on Debian 10 or 11 Bullseye
Hardened your Debian 10 Buster or 11 Bullseye by installing Fail2Ban Secuirty tool and learn how to configure it in this tutorial
How to install Fail2ban on Debian 10 or 11 Bullseye - Linux Shout