This is likely something like a FIDO token/passwordless setup of some sort (i.e. Windows Hello).
The thumbprint would just unlock the hardware device, so the thumbprint itself wouldn’t need to be transmitted to your credit issuer. This gives you full two factor authentication of your identity because you need the hardware device (something you have) and your biometric (something you are). They also often allow pins (something you know) instead of biometrics as the second factor.
In any KDE app you can connect with SFTP in the open file dialog. Just type sftp://user@server/path and you can browse/open/edit files the remote server. ssh keys+agent make things a lot easier here obviously.