Does anyone know which public search engines are not complying with robots.txt directives?

When I buy a website on Flippa or other platforms, there are no direct means to check for the existence of a hidden PBN.

This is why I am looking for a search engine not complying with robots.txt, to see if we can find some backlinks not shown in the major tools (aHrefs etc.)

Therefore, I wonder if there is a list of such search engines somewhere. I checked for Yandex for instance, but it fully complies with Robots.txt.

Thanks