
I have tested the default profile hover card on a person column in different list views and got the same result with you. It shows in the list view, gallery view and does not show in the board view.
I am afraid that the default profile hover card on a person column is not available in the board view.
Meanwhile, to get this feature more quickly, I also recommend you give the suggestion in the feedback portal and help us make improvements and build new products. Many features of our current products are designed and upgraded based on customers’ suggestion. With requirements like this increase, the problem may well be released in the future. Thanks for your understanding and support.
Feedback portal: https://feedbackportal.microsoft.com/feedback/
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