Update: After a reboot, realtime protection came back on... So this answer does not work for me. But since it proposes a new method (the registry edit) I'm leaving it here. It could help someone else. Different people seem to have success with different methods.
I also find that updating to 21H1 does not help.
For me, it was very difficult to disable Windows Defender in Windows 10 2004 (20H2). I had disabled tamper protection, but still the group policy setting kept being deleted instantly. To see this, one must restart the group policy editor. Also, realtime protection kept being turned on rather quickly when I disabled it.
I was able to overcome this with this registry setting: https://www.tenforums.com/tutorials/5918-how-turn-off-microsoft-defender-antivirus-windows-10-a.html (Search for "Turn_Off_Windows_Defender_Antivirus.reg").
This makes these changes:
So it works like this:
- Disable off tamper protection using the settings panel
- Also disable realtime protection
- Apply the registry change
- Open group policy editor
- Go to
Computer Configuration\Administrative Templates\Windows Components\Microsoft Defender Antivirus and set `Turn off Microsoft Defender Antivirus" to Enabled (not sure if this is required now)
Another option to try is booting into safe mode in order to make the changes: https://www.alitajran.com/turn-off-windows-defender-in-windows-10-permanently/