Like... what ISP would go out of their way to do that? Call me cynical, but I doubt there's an ISP that uses CGNAT who would forward a port to you. Like, they all do the total absolute minimum necessary to get you Internet access. Why would they bother creating some way to let you forward a port to your computer? No average person needs to do that anymore now that everything is cloud-based. I could be way wrong on this, but I just have my doubts...