Update

ftplugin/nftables.vim

@@ -0,0 +1,28 @@
+if polyglot#init#is_disabled(expand('<sfile>:p'), 'nftables', 'ftplugin/nftables.vim')
+  finish
+endif
+
+if exists('b:did_ftplugin')
+    finish
+endif
+let b:did_ftplugin = 1
+
+let s:save_cpo = &cpoptions
+set cpoptions&vim
+
+setlocal smartindent nocindent
+setlocal commentstring=#%s
+setlocal formatoptions-=t formatoptions+=croqnlj
+
+setlocal comments=b:#
+
+setlocal tabstop=4 shiftwidth=4 softtabstop=4 expandtab
+setlocal textwidth=99
+
+let b:undo_ftplugin = '
+    \ setlocal formatoptions< comments< commentstring<
+    \|setlocal tabstop< shiftwidth< softtabstop< expandtab< textwidth<
+    \'
+
+let &cpoptions = s:save_cpo
+unlet s:save_cpo

indent/nftables.vim

@@ -0,0 +1,21 @@
+if polyglot#init#is_disabled(expand('<sfile>:p'), 'nftables', 'indent/nftables.vim')
+  finish
+endif
+
+" Only load this indent file when no other was loaded.
+if exists('b:did_indent')
+  finish
+endif
+let b:did_indent = 1
+
+setlocal cindent
+setlocal cinoptions=L0,(0,Ws,J1,j1,+N
+setlocal cinkeys=0{,0},!^F,o,O,0[,0]
+" Don't think cinwords will actually do anything at all... never mind
+setlocal cinwords=table,chain
+
+" Some preliminary settings
+setlocal nolisp         " Make sure lisp indenting doesn't supersede us
+setlocal autoindent     " indentexpr isn't much help otherwise
+" Also do indentkeys, otherwise # gets shoved to column 0 :-/
+setlocal indentkeys=0{,0},!^F,o,O,0[,0]

syntax/nftables.vim

@@ -0,0 +1,41 @@
+if polyglot#init#is_disabled(expand('<sfile>:p'), 'nftables', 'syntax/nftables.vim')
+  finish
+endif
+
+if exists('b:current_syntax')
+    finish
+endif
+
+syn match nftablesSet /{.*}/ contains=nftablesSetEntry
+syn match nftablesSetEntry /[a-zA-Z0-9]\+/ contained
+hi def link nftablesSet Keyword
+hi def link nftablesSetEntry Operator
+
+syn match nftablesNumber "\<[0-9A-Fa-f./:]\+\>" contains=nftablesMask,nftablesDelimiter
+syn match nftablesHex "\<0x[0-9A-Fa-f]\+\>"
+syn match nftablesDelimiter "[./:]" contained
+syn match nftablesMask "/[0-9.]\+" contained contains=nftablesDelimiter
+hi def link nftablesNumber Number
+hi def link nftablesHex Number
+hi def link nftablesDelimiter Operator
+hi def link nftablesMask Operator
+
+syn region Comment start=/#/ end=/$/
+syn region String start=/"/ end=/"/
+syn keyword Function flush
+syn keyword Function table chain map
+syn keyword Statement type hook
+syn keyword Type ip ip6 inet arp bridge
+syn keyword Type filter nat route
+syn keyword Type ether vlan arp ip icmp igmp ip6 icmpv6 tcp udp udplite sctp dccp ah esp comp icmpx
+syn keyword Type ct
+syn keyword Type length protocol priority mark iif iifname iiftype oif oifname oiftype skuid skgid rtclassid
+syn keyword Constant prerouting input forward output postrouting
+
+syn keyword Special snat dnat masquerade redirect
+syn keyword Special accept drop reject queue
+syn keyword Keyword continue return jump goto
+syn keyword Keyword counter log limit
+syn keyword Keyword define
+
+let b:current_syntax = 'nftables'