If you want to be in the telephone directory, you have to make details - your name and your number - available. If GDPR is going to force phonebooks to be empty then it's simply silly. Publishing those details for your own benefit is literally the point of it.
You can, of course, choose not to be in the phonebook. Or put a business name rather than a personal one. It's then your problem to make the number usable, presumably by advertising it elsewhere or to a closed group.
Domains should be exactly the same. You want a public advertisement of how to reach you, you permit your contact details to be known. You want a private IP address, that's your problem : you don't need a domain.