I am using a proxy that limits it access by IP or hostname (so no port forwarding here).
I was using a dynamic dns domain updated by the 4G modem. That was working fine until I switched providers, and the new provider uses CGNAT. So now the modem is not getting its public IP, and updates the domain with the wrong one. There are no parameters to set client-side except for the service provider / domain / password.
Running a more flexible client on a machine inside the network is problematic (this is a wifi network with clients such as iPads, etc...). I'd rather not add something like an rPi just for this purpose (it makes the solution a bit less movable).
So is there a dynamic dns service provider where you can setup the domain to ignore the "myip" parameter of the update request?