How does one specify the subnet mask when adding a rule in nftables?
A slash immediately following the specified ip address results in a syntax error.
nft add rule ip filter input 0.0.0.0/24 drop
results in
Error: syntax error, unexpected /
(OS: Debian Buster: nftables v0.9.0)
Your syntax isn't quite right. You are missing "ip saddr" after input.
nft add rule ip filter input ip saddr 0.0.0.0/24 drop