I want to put a vanilla android smartphone on noname, what to read, where to start?

Question

Android

Manufacturers overload the phone with their "cutes", and the Chinese - in general, embed adware, and then, probably, backdoors. Although iron seems to be quite good.
I’m ready to spend time studying the issue, but I won’t find a decent consistent presentation, I picked up fitfully, in my head porridge.
There is, of course, another plan "B" - to clean the existing firmware to a shine, but this is just an extreme case.