iOS, iPadOS and tvOS 14 support MDM profile to set encrypted DNS requests (DNS-over-HTTPS and DNS-over-TLS) on cellular and Wi-Fi connection.
To install, open this page from your device and click
Raw on the one of your choice in the GitHub page.
Then continue installation in Settings app.
Browse https://126.96.36.199/help after installing to check it.
If you want to switch after installation, go to Settings > VPN and Network > DNS
Automatic makes your device use DNS of your ISP.
Go to Settings > General > Profiles and remove the corresponding profile.