Welcome to the world of Carrier Grade NAT. 100.64.0.0/10 is reserved for this.

If you are lucky, you also have an IPv6 address. The catch is you need IPv6 on the client-side too.

A VPS or similar running wireguard and a proxy might bridge the gap.

It might also be possible to ask your provider for some port forwarding. Probably not, but check anyway.

Good luck!