If the August was too loud for you, I think you’re out of luck with the list as you gave it. Every smart deadbolt lock has a motor that is physically moving the deadbolt. And those make noise, with the August being among the quieter ones.
There is an alternative as far as quiet goes which is to go with an electric strike instead. These don’t have a motor, they have an electromagnetic release for the door latch. They would be quiet and they can be made to work with voice assistants, but you aren’t going to be able to keep your existing key, because it won’t release the magnet.
If you’re interested in looking at the electric strike option, here’s a project report from one member who did that:
But unless @rboy knows of something, I don’t think you’re going to find smart lock that’s much quieter than the ones you’ve already tried. 