If you were using the default port 25565, you could simply have a DNS A record pointing to the server IP. But since that is not the case, you have to additionally set up a SRV record in your DNS. NOIP describes what this is and how to set it up on their service here, but it will of course differ for your DNS provider.
This still requires that the Minecraft server port is directly accessible from the other clients, but it sounds like that is not the problem
In my experience, Chat GPT is much better at the general programming patterns and concepts than specific API implementations. Especially less commonly used ones, where it often gives a solution that only looks reasonable but uses the totally wrong methods. I guess it's similar with scraping the HTML of the Ubuntu releases page to get the latest torrent. It doesn't know the exact HTML layout, so it guesses what is a likely one, even though it is wrong.