I assume you found this already? Discussion of local control of Tuya Smart Wifi devices without flashing firmware
I am still using my hybrid cloud/local setup.
For something simple like a relay it probably only have one or two commands to turn on/off and that's going to be it. You could probably use a custom local only driver for it.
The down side of the local driver seems to be is it only supports one connection, so if you use the Tuya app at all, or possibly even Alexa via Tuya cloud it is unreliable.
I can dig up some further info depending on what you want to try.
