How to disable adding iptables rule?

Question

iptables

I took a server with a pre-installed image of Ubuntu 16.04 immediately after starting, there is such a rule in iptables-save

-A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to-source ХХ.ХХ.ХХХ.ХХХ

If I understand correctly, it is added there by some script. Instead of this rule, I need a completely different one.
-A POSTROUTING -s 10.0.0.0/8 -o ens2 -j MASQUERADE
Otherwise, my VPN refuses to give the Internet. How to do it right?

Answer 1

In debian (I think it is similar in ubuntu) the start script for iptables is placed in /etc/network/if-up.d/.

Answer 2

I first look at the table and chain numbered
sudo iptables -L -nv --line-numbers
and then remove the rule number
sudo iptables -D (table, chain) (rule number)
sudo iptables -D INPUT 3