There is an alternate verification method using an API key to your DNS provider, if it’s a supported one. That method doesn’t need any IP to be assigned (doesn’t care if there are A/AAAA records or where they point because it can verify the domain directly).
deSEC.io is a good example of a good, reputable and free DNS provider that additionally allows you to manage API keys. The catch is that they require you to enable DNSSEC (their mission is similar to Let’s Encrypt, but for DNS).