Difficulty
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Very easy
How to disable DOH
Microsoft Edge
Go to Settings → Privacy, search, and services → Use secure DNS to specify how to lookup the network address for websites, and click on the switch to disable it.
Mozilla Firefox
Go to Options → Network Settings → Settings, find the Enable DNS over HTTPS option and disable it.
Google Chrome
Go to Settings → Privacy and Security → Security → Use secure DNS and click on the switch to disable it.