To break the domain privacy, you can check the archived whois data.
Older data can not be found on archive.org. But there is a website that can help you see some snapshots of the previous whois data.
Which website can help you see the archived whois detail?
whoisxy.com, this website will show you some snapshots of previous whois data. But the condition is that the detail must not be secured while purchasing the domain.
This website shows you archived data of whois. If the data is not archived, it can not be shown.
What detail can be seen?
You can see the email id of the domain owner.
If you know of any other website offering the service, please let me know in the comment. I shall add that detail in this article.