I have a few own blacklists, hosted on my own website.
This website is placed behind the OpnSense NGINX plugin.
When I create an alias IP table (on another firewall) with this (https or http, both the same) url, it won't load any ip.
When I create a portmapping on port 81 from the WAN to the website on port 80, bypassing NGINX, everything works as expected.
So it looks like the iptables and NGINX won't play together.