Asklemmy

The Windows Hello camera enumerates under Linux as just another webcam that activates the flashing LEDs when it turns on (I've found a number of neat uses for this, including having a ridiculously low gain IR camera that I can just use for whatever and have what would be a surprisingly good emulation of the Wii sensor bar for use with Dolphin if it weren't constantly flashing on and off), and there is software (Howdy) for using it to sign in. Unfortunately, signing in with your face of course precludes using your password for decryption, meaning that after you start some applications you'll be prompted to type your password anyway to unlock your system keyring, and perhaps more importanty SDDM isn't smart enough to interface with fprintd/howdy properly and doesn't even try to activate the biometric sensor until you type something in the password box.

(Also, hilariously, because of how I set it up initially to accept my face instead of a password for sudo, I couldn't configure it to check whether the terminal was remote, so when I ssh'd in and tried to sudo, it turned on the hello camera however far away that was and looked for my face, only prompting me for a password after facial rec timed out.)