You don't need to read it haha
It's always a struggle to share links in DMs since I don't want to pressure people into reading the content.
It's detailed but I am wondering if it's still worth the time. 15-20 minutes is a lot. Maybe the same could be explained in less time, idk.
But I think the iptables primer which is at the top is a good resource to get a good grasp on iptables.