Yeah, I just discovered my ISP (WebPass) has exhausted their IPv4 allocation [1] and is transitioning residential customers to private IPv4 addresses, and I'm not really sure how to set up a VPN on IPv4 now. I guess I need to set up a tunnel over IPv6 somehow?
I (hope to) see CGNAT as the stick - with v6 being the carrot that allows point-to-point apps and personal hosting to work reliably again.
That requires the ISP to offer v6, of course. I'm on Comcast which, say what you will about them, has been years ahead of everyone else for carrier-grade v6 support.
1. https://webpass.net/blog/ipv4-exhausted