go to google play look for VPN HOSTS... its an app that creates a vpn on your phone and uses the hosts file you provide and blocks ads just fine.. been using this since it was created and it works great.. no root needed, its a virtual hosts file ...
Rooted stock rom is easy if you have this already and sampwnd zip. Or close to it. Go find your system.img you want. Flash it with sampwnd. Then after flash from Odin your csc and cp. First csc then cp. IDK why but it works. Almost fully stock and...
I had same issue with my S6, all I did was shut off the connection optimizer and internet works great, faster than ever.
That's the same build I have after updating my device. Have you had any luck rooting yours yet?
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I have yet to Root the phone, been waiting and think I will try soon, as I might not need Samsung Pay, been ...