A bit of a tangent, but something like PowerDNS authoritative server comes with an API[0] that can be leveraged for similar functionality to what Cloudflare provides.

Decentralization of the internet has to start with Authoritative DNS. I know it's not free to host an authoritative server like this on a VPS, and there are DDoS considerations. But the flip side is that DNS is a metadata protocol and contains a wealth of information that anybody privacy focused should think twice about. It's also an incredibly powerful and important protocol to understand.

[0] https://doc.powerdns.com/authoritative/http-api/index.html