When it comes to packet filtering on Linux, Nftables (a successor to Iptables) has matured sufficiently in recent years for it to be considered the default tool to use today. However, Iptables is still widely used in modern systems (e.g., Debian buster),  with it often being “emulated” by using Nftables as backend, whereupon it becomes merely an alternative syntax to Nftables for defining packet...