If your smart lock is connected to a voice assistant, be sure to use a PIN to unlock it with voice commands. It's a stretch, but it is possible to create workarounds with IFTTT to avoid using the PIN.

While setting up a lock screen PIN on your Android or iPhone, there's always the fear that you might forget it one day. That's especially true if you usually rely on quicker methods without a password ...

Google’s system basically keeps all the security of a SIM PIN, while removing all the inconvenience. Just make sure you jot down the Android-managed PIN somewhere secure, in case your phone ever dies ...