# Install nftables
doas apk add nftables
# List tables (default table is `inet filter`)
doas nft list tables
# Add to the default inet filter (allow ssh server port 22)
doas vi /etc/nftables.d/ssh.nft
cat /etc/nftables.d/ssh.nft 
table inet filter {
        chain input {
                tcp dport 22 accept
        }
}
# Load nftables config
doas rc-service nftables restart
# List rules
doas nft -a list table inet filter
# Load rules at boot
doas rc-update add nftables boot