How to add a DNS Filter to an iPhone or iPad - iOS version 12.x

One of my favorite DNS Filters comes from a company named CleanBrowsing.

CleanBrowsing:

Security Filter 185.228.168.9: Malicious domains blocked (phishing, malware). Adult Filter 185.228.168.10: Adult domains blocked;

Search Engines set to safe mode; +Security Filter Family Filter 185.228.168.168: Proxies, VPNs & Mixed Adult Content blocked;

Youtube to safe mode; +Adult Filter

There are many DNS Filters and some work better than others. A Google search will provide several well tested comparisons.