Help finding a Quiet Smart Lock

[RBoy (www.rboyapps.com - Making SmartThings Easy!)]

You can check out the table in this post which compares locks features:

[EDGE] Universal Enhanced Z-Wave Lock Driver for Schlage, Yale, Kwikset, IDLock, Popp, Danalock, August Pro, Keywe, Philia, Samsung

A “future proof” Universal Enhanced Z-Wave Lock driver This driver is enhanced to fix bugs in the stock ST ZWave Lock driver, include patches for bugs in lock firmwares and bring out additional features for Schalge, Yale, Kwikset, IDLock, Popp, Samsung, Delaney, August Pro, Danalock, KeyWe, Philia, Vivint, Locstar etc zwave locks (see below for a full list of models and features). This works with all ZWave locks and newer ZWave Plus locks (see below for a list of locks tested). It discovers/learns the lock features and automatically configures them. If a feature is not supported by the lock it will not show up or say Unsupported. You need SmartThings Smart Lock Guest Access (SLGA), Advanced Web UI or a SmartApp like Lock User Management (LUM), Rental Lock Automater (RLA) to program user …

As far as keeping your existing key, that’s going to be an issue with any brand as they prefer their own keys. You could try rekeying it through a locksmith and see if they do it for different brands.
Without keypads in the US your best bet would be the August but you’ve ruled that out. You can check out the Yale and Schlage brands. I can say that deadbolt versions will have motor noise (Yale less the Schlage). If you don’t want motor noise look for the electronic latching versions from Yale and Schlage like the Schlage FE599, they’re very silent. As for Alexa, you will need either ZigBee for direct pairing or you will need to connect SmartThings to Alexa but you’ll have limited control of these locks through SmartThings for security reasons.

What controls are you looking for from Alexa?