Prevent ISP DNS Hijacking

DNS is not the only way to block sites. There is also port blocking, IP address blocking (though not very feasible and effective in the age of cloud as @Robert said) and protocol blocking (with DPI). See a brief description of censorship techniques here. But if you are sure it's only the DNS your ISP is intercepting, you can use encrypted DNS:

• Android 9 introduced Private DNS (DoT) (under Network Setings) which encrypts whole DNS traffic both for WiFi and Mobile Data. Hotspot traffic is an exception though.


• If you are concerned about web browser only, Firefox does have built-in settings for DoH.


• If you have a rooted device and you want more control or want to do logging, blacklisting etc. or want to use encrypted DNS for hotspot network too, dnscrypt-proxy is a better option. It supports both DoH and DoT. See how to set up dnscrypt-proxy as an init service on Android with least privileges.