rdap is nice when it's available.

    cargo install icann-rdap-cli
    rdap -O json ycombinator.com| jq .nameservers

(or brew install, etc., depending on your os and tooling). The jq formatted output is a little more verbose than the whois one, but three cheers for a well-specified machine-parsable format. (and rdap has a pretty-printed format output also)