nftables - #Debian Wiki
▻https://wiki.debian.org/nftables
NOTE: Debian #Buster uses the #nftables framework by default.
Starting with Debian Buster, nf_tables is the default backend when using #iptables, by means of the iptables-nft layer (i.e, using iptables syntax with the nf_tables kernel subsystem). This also affects ip6tables, arptables and ebtables.