Hey!
Some days ago I created this issue at GH: fail2ban: "sshd-filter" is outdated, which triggers (wrong) warning in "aggressive" mode · Issue #478454 · NixOS/nixpkgs · GitHub
Because there is/was no reaction, up to now and the maintainer @lovek323 IMHO *seems inactive (*at GH and this forums) I will kindly ask the dev community to have a look …
Tnaks in advande and KR!