iOS 11: How to change DNS settings for cellular/mobile data?
Build your own VPN using OpenVPN &amp; easy-rsa on a digital ocean cloud server ($5/mo for cheapest VM &amp; 2TB monthly transfer), configure VPN to tunnel/forward all traffic, set up Cloudflare 1.1.1.1 on VPN, then use Apple Configurator to set an always on VPN connection. 

Can confirm this is how I do it, I set up Ubuntu 16.04 server instance and the above and never shut my vpn off.