I did start with Yacy. First I would bould something thet search a list on Google or so and the just follow links forever. Finally I just found Yacy a P2P search. I did run it for a couple of years.

https://yacy.net/

I would guess Tor, I2P, Freenet, GNUNet.

But also configuring or avoiding certain other software: https://spyware.neocities.org/articles/index.html