Sometimes we disappointed to use isp's dns resolver. whatever the reasons, since Android 9 (Pie) and later versions, user can change his/her android phone to use Private DNS. Only one DNS server can be used, it does not support multiple DNS resolver!
Original list was taken from https://www.geeksforgeeks.org/android/how-to-enable-private-dns-on-android/ with additional text.
Private DNS Hostname List for Android
- Google DNS: dns.google
- Quad9: dns.quad9.net
- Cleanbrowsing DNS: security-filter-dns.cleanbrowsing.org
- Open DNS: dns.opendns.com for dot, https://doh.opendns.com/dns-query for doh, 208.67.222.222
- NextDNS: your-id.dns.nextdns.io 45.90.28.0 (custom IPv4) require registration to get id and proper full qualified hostname
- Cloudflare : cloudflare-dns.com 1.1.1.1
Please check their website or use search engine for more detail and update information.
When you use private DNS in public network, your mobile phone will use your private DNS resolver that have you define. It won't use DNS from public access point. This will prevent you from "man in the middle attack".
Warning: You also can bypass country blocked to reach your desire web. You don't need vpn if private DNS can solved country limitation.
