Vercel currently uses the Anycast methodology for DNS and routing. This solution allows those using a custom domain to verify it without requiring a change in nameservers.
To use a domain with Vercel using an A record, you need to add it with the value
18.104.22.168, which is the IP for the Vercel network. If you already have a CAA record in your root domain, it is also necessary to include a CAA record with the value
"0 issue letsencrypt.org".
If you followed the instructions above successfully, your domain will be available for use on any Vercel project that you own.