- Download Group Policy templates for your Firefox version here
- Copy *.admx files to C:\Windows\PolicyDefinitions
- Copy *.adml files to from en-US to C:\Windows\PolicyDefinitions\en-US (or other language folder if applicable and available)
- Launch gpedit.msc (gpedit.msc is not available on Home versions of Windows, if you have that, I recommend using third party Group Policy editor like PolicyPlus)
- Navigate to Computer Configuration -> Administrative Templates -> Mozilla -> Firefox -> DNS Over HTTPS
- “Enabled” -> Disabled; “Locked” -> Enabled.
Disabling Firefox’s DNS Over HTTPS via Windows Group Policy