I have leaa.rn domain in namecheap and want to move it to Cloudflare. I see an error that “We were unable to identify leaa.rn as a registered domain. Please ensure you are providing the root domain and not any subdomains (e.g., example.com, not subdomain.example.com)”
You cannot use Cloudflare with so-called handshake domains. They are not real domains and exist completely outside of the DNS hierarchy. Since they do not use DNS, there is no way to use them with Cloudflare.