FWIW I looked up my own domain name through lookup icann with .eu tld, it shows me exact same thing,
No registry RDAP server was identified for this domain. Attempting lookup using WHOIS service.
Failed to perform lookup using WHOIS service: TLD_NOT_SUPPORTED.
This probably means they literally don’t support looking up .eu tld domains.
I don’t know the other site, so can’t tell what my domain name whois info is