@S716: If you don't want to use Biometrics on your Lock Screen, or you want to disable the Lock Screen security completely, then please head to Settings > Lock Screen > Screen Lock Type > Enter your current PIN, Pattern or Password. From here, select Swipe or None, and toggle off Face and Fingerprints at the bottom of the screen.
Smart Lock keeps the phone unlocked under certain conditions, however you do need to register a Lock Screen Type in order to use it. As an alternative approach, head to Settings > Biometrics and Security > Samsung Pass, as this allows you to use Biometrics to verify your identity on supported apps. I hope this helps.
