Using Microsoft Remote Desktop (version 10.8.4 (2111)) on a MacBook, when signing into a workspace I'm presented with my options, but if I select Security Key the login page goes grey and just hangs ...
I have a similar problem: I need to authenticate with my security key on an app in a RDP session from macOS but it looks like the security key is not being passed through. I have selected smartcards to pass-through as this seems the most appropriate option and the only one making sense. But obviously it does not work.