TikTok is basically a maximally addictive piece of spy software disguised as a social media platform that people voluntarily install. The app is not actually free, since you pay with your privacy.

I strongly suspect that the data harvested by TikTok and others is only limited by what's technically feasible at the moment. As soon as more technical possibilities become available, they'll harvest more.

Here's the information that TikTok collects about, as mentioned in their terms of service:

"We collect certain information about the device you use to access the Platform, such as your IP address, user agent, mobile carrier, time zone settings, identifiers for advertising purposes, model of your device, the device system, network type, device IDs, your screen resolution and operating system, app and file names and types, keystroke patterns or rhythms, battery state, audio settings and connected audio devices. Where you log-in from multiple devices, we will be able to use your profile information to identify your activity across devices. We may also associate you with information collected from devices other than those you use to log-in to the Platform."

https://www.tiktok.com/legal/privacy-policy-us?lang=en

Source

https://rumble.com/v1eewxv-joe-rogan-reviews-tiktoks-crazy-terms-of-service.html?mref=2hzb1&mrefc=10