I've used the Feedback Hub for this purpose in the past, as there's a category for Windows Security (or maybe Windows Defender).

The only other thing I can recommend is using the Give us feedback link on the Protection History page of Virus & Threat Protection of Windows Security.
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Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042  

The depths of denial one can be pushed to by outside forces of disapproval can make you not even recognize yourself to yourself.

       ~ Brian Vogel