If somebody learns that such-and-such DynDNS URL is mine, they can always do a DNS lookup to find my current IP address. They can:
- find my approximate physical location
- regularly scan ports on my IP and wait for me to accidentally expose a service I didn't mean to
- track me in any access logs they have access to
They can, and do, do this with or without DynDNS.
Do you mean by getting the information from Cloudflare, or some other way? With DynDNS though, finding out my IP is trivial and does not require any special powers or skills, it is just a DNS lookup.
PS. Just re-watched your matrix LED pendant video. It is so well done, both the project, and the accompanying video!