@Dominique DUCHEMIN
Thank you for posting in Microsoft Q&A forum.
1)When you install Endpoint Protection manager role on your primary site server, if your server have not installed the windows defender, you may meet this Error code:0x8004FF73, the component " Endpoint Protection control manager” is critical, but the server is able to apply the endpoint settings without issues. It's recommended to add the windows defender feature and reboot the server, then re-deploy the Endpoint Protection role.
2)About the Microsoft Defender Antivirus compatibility, you may refer to:
https://learn.microsoft.com/en-us/windows/security/threat-protection/microsoft-defender-antivirus/microsoft-defender-antivirus-compatibility
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