OnePlus OxygenOS built-in analytics
I have absolutely no doubt there is some data centre in Shenzhen full of my Huawei phone metrics! 
I think this is the biggest issue with android phones, they are full of potential data leakages like this. Privacy is definitely a concern and a pull factor to getting an iPhone again. There is a lot to be said for a company that is focused on hardware and not on serving content to that device.
Then again it's also a reason to get a Pixel2, I feel I can trust Google with my data more than some other android manufacturer or reseller. Sure they'll serve me more adverts, but it's to some ends at least.