Your issue has always seemed to be the inability to reach the github site. Run some tests from the router.
Code:
nslookup raw.githubusercontent.com
ping raw.githubusercontent.com
traceroute raw.githubusercontent.com
curl -v https://raw.githubusercontent.com/Adamm00/IPSet_ASUS/master/firewall.sh -o /dev/null
Don’t bother with USB replacement or double NAT. If you can’t reach the download site, none of it matters.
Do you live somewhere in the world where an ISP or government would want to block github? Or a country known for bad internet guys and so maybe github is blocking your country or ISP’s addresses?
Can you reach the normal github site from a PC (without a VPN)?
Skynet - Advanced IP Blocking For ASUS Routers Using IPSet. - Adamm00/IPSet_ASUS
github.com