If you only need to worry about the IP changing, then your ISP is not using NAT, or CGNAT as it is better known. I’m pretty sure that you can also use port forwarding, which is not commonly available under CGNAT.

Accessing your home network that is kept inside a NAT by your ISP, without you having to acquire an online server somewhere.

That sounds like a SystemD responsibility, given that it is an OS abstraction layer.