Hmm back in the day I used to be "connectible" virtually no matter what ISP I used and was able to seed properly without a VPN.
I am pretty sure Optimum, COX, and Verizon were all seedable ISPs but I guess they all changed their shit at some point in the recent few years?

I am not able to seed no matter what I do, port forwarding, trying to get a static IP (which most of them block now also)

I guess I'm just gonna have to take the dive and buy a VPN?