Tuya zigbee local key

Hi all,
I have Tuya Zigbee components (Tuya ZigBee 3.0 Module de prise de vie intelligente télécommande sans fil, fonctionne avec Echo Alexa Google Home Assistant vocal bricolage relais), home assistant and a dongle SonOff efr32mg21.
I read some topics to integrate Tuya components to Home assistant by using Tuya smart app (local devices detected&added) then Tuya IoT Platform linked to the smart app to get the local key of each device (info from @rospogrigio for example).
Each demo is done with Tuya devices with Wifi connexion (not full Zigbee)
I understand and seems good.

But I don’t understand one thing.
I have no official Zigbee hub and I can’t add my local Zigbee devices to the Tuya smart app (no detection because my smartphone is not linked to a Tuya zigbee hub). So I can’t get my local zigbee devices in the Tuya IoT Platform and I can’t get the local key.

Where is my mistake?

thanks

If you want to use your devices over tuya cloud, you need cloud account.

If you want to use your tuya devices with your local sonoff usb dongle, you just need to add your devices with it as other branded ones as long as your device is supported. Nothing different