Holesail.io can be used as a replacement of DNS, it allows you to use a dynamic IP while keeping the connection string static, while using no DNS system at all.

Disadvantages I can think of: iOS version of holesail pauses as soon as it goes into background so Nostr will work only when the app is open (I am looking for a workaround), there is no web version of Holesail.

But Desktop version of Nostr clients on Windows, Mac, Linux and even Android can utilise Holesail to run and connect to a Nostr node based on a "connection string".