Hello!
I’ve already thought about it myself. In theory, it should not be difficult - to add in folder /etc/fail2ban/action.d file with something like
actionban = cscli decisions add --ip < ip > --duration < duration > --reason < reason >
And then call the jail.local.
I am now carefully reading the documentation, I just started to master CrowdSec, so I am in no hurry to implement something - I suddenly subtract a better solution.