On more thing in the fail2ban log. Seems like fail2ban cannot hook correctly into the iptables:
Code
2018-11-30 20:36:17,390 fail2ban.action [15638]: ERROR iptables -w -N f2b-ssh
iptables -w -A f2b-ssh -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports ssh -j f2b-ssh -- stdout: b''
2018-11-30 20:36:17,391 fail2ban.action [15638]: ERROR iptables -w -N f2b-ssh
iptables -w -A f2b-ssh -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports ssh -j f2b-ssh -- stderr: b"iptables v1.6.0: can't initialize iptables table `filter': Table does not exist (do you need to insmod?)\nPerhaps iptables or your kernel needs to be upgraded.\niptables v1.6.0: can't initialize iptables table `filter': Table does not exist (do you need to insmod?)\nPerhaps iptables or your kernel needs to be upgraded.\niptables v1.6.0: can't initialize iptables table `filter': Table does not exist (do you need to insmod?)\nPerhaps iptables or your kernel needs to be upgraded.\n"
2018-11-30 20:36:17,392 fail2ban.action [15638]: ERROR iptables -w -N f2b-ssh
iptables -w -A f2b-ssh -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports ssh -j f2b-ssh -- returned 3
2018-11-30 20:36:17,393 fail2ban.actions [15638]: ERROR Failed to start jail 'ssh' action 'iptables-multiport': Error starting action