Re: then disable the least significant part of it.
If you've disabled the Google Play store and sideload your apps, that puts you in a sub-1% group of users who would bother to go that far. Even if you're only using it for Amazon Prime Video, that's still data served by Amazon; they don't need to get through your firewall to track it. Some things they can do passively and remotely to build an advertising profile:
- Extrapolate your gender, age group and persona (including the fact that you have a firewall, and are tech-savvy and interested enough to disable the Play Store).
- Build a profile of your interests, socioeconomic and demographic data by collating what you watch, when you watch it, where you are when you watch it (from WiFi if nothing else) and also what you DON'T watch (including skipping over, pausing or rewatching movie scenes).
- Track finger swipes, pauses, zooms and scrolls to further enrich your profile.
- Link your data to other people's data around you; for example if somebody else logs into or uses your tablet, or you regularly log in at the same time as somebody else, inferences can be drawn from this about your living circumstances (married, kids, how under the thumb you are and so on) - and then cross-link their data with yours.
All of this was possible (and was being actively used) in 2015 when I was involved in this kind of software (one of my clients was Sterling, who used data such as this to drive their Configure/Price/Quote dynamic pricing algorithms). I'm absolutely certain much more has become possible since then.