Hi, @Duchemin, Dominique
Thank you for posting in Microsoft Q&A forum.
Like you said, System Center Endpoint Protection requires Windows Defender feature from Windows Server 2016, 2019 and 2022, because Windows 10 or later devices don't need to have the Endpoint Protection agent installed.
So, we don't need to uninstall System Center Endpoint Protection agent when we don't want to manage it, we just need to modify the client setting, set the "Manage Endpoint Protection client on client computers" to "No". And delete the Antimalware Policy for this device.
It doesn't matter to remove or keep the Windows defender feature.
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