This is neat and interesting, truly, but the classic “what now?” emerges. I guess the only answer is “throw out my iPhone”? Otherwise this kind of seems like a circuitous ad to make people get worried and download Psylo, which I see has in-app purchases. I’m not trying to come at you here, but it’s just hard not to feel suspicious online these days.
The only way to prevent this right now is to avoid installing apps that are doing this.
Don't install apps outside trustable apps that don't embed tracking. Even if you cannot uninstall every app, the fewer you have, the less cross-app tracking. Also donate to and consider installing privacy-conscious alternative phone OSes. They may not have closed all holes (yet), but at least their incentives are aligned with yours.