My cousin told me his phone listens to him and now I can't unhear it

Picture this: you buy a burner phone, make a fake account, sit there whispering "zero turn mower" at it for an hour, and then you get ads for... zero turn mowers. Congrats, you just proved your phone is a tiny spy that also happens to know you're a weirdo. But for real, the setup is tricky because a clean phone still has Google or Apple baked in, and a fresh account on the same wifi and IP can still get linked to you. You'd basically need a whole separate device, new sim, new email, and to never log into anything you already own on it. Good luck explaining that purchase to your cousin without sounding like you're building a bunker.