I think I got this sorted out.
If you replace the white August module with the green Yale module, you cannot continue to use the August app to control the lock and/or get status of the door state (open/closed).
I left the batteries in the lock and swapped the white module for the green one. I did not reboot it.
In the SmartThings Classic app, I was able to add the lock.
I can control the lock in the classic and new apps.
You won’t be able to use the door sensor (open/closed) that came with it, unless there is additional device handler I’m unaware of.
Just thought I’d share that.