Here is the long version.
Pair each device with the SmartLife or Tuya apps.
In the SmartLife or Tuya apps create separate ON and OFF “tap-to-run” automations (scenes) for each device you want to use in SmartThings.
In SmartThings run the SmartLife integration under add a device by brand. Do NOT use the Tuya integration.
When you go back to the devices tab in SmartThings you will find ON and OFF switches for each device possibly under No Room Assigned.
They will say they are connected. You can wake them up by turning them on and off in the to mobile app. You only need to do this once for each imported switch.
Create a virtual switch in SmartThings using the Edge Driver “vEdge Creator”, API Browser+, or SmartThings Labs.
Using SmartThings automations create 2 automations. One will say toggle the “ON” scene when the virtual switch is turned “ON”. The second will say toggle the "OFF” scene when the virtual switch is turned “OFF”.
I have been using for several year with no issues.
FYI: If you open each device in the SmartLife/Tuya app and hit the edit icon (pencil) it will list the “3rd party controls” that are available for that device.
I have a number of SmartLife devices. Most list Alexa and Google controls. Only a few list Smartthings or IFTTT.
Any SmartLife/Tuya Tap-to-Run (scenes) you create get integrated with SmartThings.
Updated on 5-12-2023 & 10-07-2024 to be consistent with the new ST platform.