If you try to enable ufw firewall, get this error: Iptables v1.8.4 (nf_tables): Could not fetch rule set generation id: Invalid argument
CT (Ubuntu Ubuntu 22.04.2 LTS) on proxmox 7
Fix:
apt install iptables
update-alternatives --set iptables /usr/sbin/iptables-legacy
update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy
apt-cache policy nftables
If nothing works, then run:
ufw reset