Both the KDE lock screen and SDDM (partially) support fingerprint readers for authentication, but it is not well integrated into the KDE settings, and the UX is not very streamlined.
I myself have not managed to get SDDM to work in a good way, and the lock sccreen requires extra keypresses to work.
I am wondering if anyone is working on this and what the outlook for Plasma 6.2 is?
/Jaybe