I've done some search ads for https://www.nslookup.io in the early days, but I don't think it has done much. I don't track users, so I don't know if it got me any returning users. In any case, facebook's recent downtime [1] and a well-received blog post [2] brought in much more traffic.

[1] https://plausible.io/nslookup.io?period=custom&from=2020-12-...

[2] https://plausible.io/nslookup.io?period=custom&from=2020-12-...