Hello,
i read the post and understand that no solution found yet.
I'm experiencing the exact same issue you had\have?, i think mine is a bit worse from what i read,
i cant even use Facebook legitimate URL links that open in the Facebook built in browser,
it will popup every 3 pages, always popup at the first link clicked.
Although, i found something useful, if you config google chrome not to allow java script it will not happen again, but some sites will not work.
My solution for now is to use some built in ad-block browser (mine is opera mini and its working but its not a good browser).
I tried every bits of the solutions running on posts but with no luck,
even installing custom OS with cleaning the entire .img files of system, radio etc...completely clean.
I'm thinking it's coming from one of the accounts that is synced, like google photos?maybe some pic is infected or something?
I have this thought cause i'm pretty sure after clean installation when i didn't prompt for any login accounts and chrome was OK, no ads,
once i entered google account problem re-occur.
It will happen on any legitimate link like news site, eBay, Facebook, any site will get a popup.
what do you think?
Thanks