I have written a configuration profile. This means that all DNS requests on your iPhone/iPad/iPod Touch are routed via Quad9 DNS-over-TLS.
After downloading the file, you have to unzip and open it. Now you will get a message that a profile has been loaded.
Open your settings --> profile loaded ->> install. Now you have to enter your code to confirm. Then go to Install.
Under Settings ->> VPN and Network you will now find DNS Quad9 DNS-over-TLS which is also directly activated.
You could check this on https://www.dnsleaktest.com/ just choose the standard test.
This now spits out IP, hostname, ISP and country from your DNS server Quad9.
Here is the link to https://www.quad9.net
If you want to delete the configuration profile, you can remove it via Settings --> General --> Profile --> Quad9 DNS-over-TLS --> profile and delete.
sorry for my bad English and have fun with the configuration profile.
