As for some ancient Smart Life app versions it was possible to extract the local keys directly from a rooted Android phone. Unfortunately this doesn’t work anymore since quite a while.
The control centre for tuya devices is surley located in the tuya cloud. The Smart Life app is only communicating directly with tuya devices during the pairing process. Just cut off your internet connection and try to switch a tuya device from your phone using the same SSID as your tuya devices. It wont work properly anymore.
Tuya based devices are obviously “reporting home” their status at regular intervals. This happens also to report back to the Smart Life app on the phone whether their actual status is online or offline. If they are considered offline for whatever reason by the tuya control centre (i.e. you have successfully blocked all ingress/egress connections from/to the Tuya Cloud, or you have an internet blackout, or the tuya device has freezed) you’ll receive that “Device Offline”-message sent onto your phone.
Although I am quite careful about where “my” data is going I did not block tuya devices from communicating with the Tuya Cloud. The main reason for installing Tuya Local to HA on my side (replacing the original Tuya integration) is because internet blackouts are happening frequently here and during those cut-offs automations controlling tuya based devices were not working reliably anymore. Even worse, if the internet connection was down for an extended period of time I had to re-pair most of the devices thereafter with the Tuya Cloud. Very annoying.
The second reason why I have installed Tuya Local is the time for the status updates from tuya devices to the Tuya Cloud back to HA. These staus updates can take up to >20 minutes (take a look here and here for an explanation of the latter). If you have automations based on the staus of tuya devices they are getting pretty much useless.
In short: If you are not too concerned about the fact that your tuya devices are reporting their actual status to the tuya control centre within the Tuya Cloud just let them do so. As for realibility install Tuya Local onto HA replacing the Tuya intergation which comes with HA. This way you’ll get the best out of two worlds: Internet cut-offs doesn’t have any impact on your automations anymore, status updates of tuya devices are happening instantly and in the rare case your HA installation gets unresponsive you can still control your tuya devices through the Smart Life app.