DNS/Androidについて、ここに記述してください。

Android Configuration instructions for OpenDNS 

https://support.opendns.com/hc/en-us/articles/228009007-Android-Configuration-instructions-for-OpenDNS



These instructions only work for Wi-Fi connections because Android does not allow you to change the DNS servers when connected to cellular networks. 

Wi-Fiごとに決められるらしい。

How to make Android use the DNS server of your choice　　Stephen Schenck


https://www.androidpolice.com/2018/04/20/make-android-use-dns-server-choice/