Since a few weeks I have local tuya installed. Today I got an error :We found a custom integration localtuya which has not been tested by Home Assistant.
So set up failed today. What can be the cause of that.
Second : I know it has been asked before but cannot find it : Is it possible to use both the tuya integration and local tuya ?
That custom message is most likely a warning only and not an error.
The complete line should be something along
“WARNING (SyncWorker_0) [homeassistant.loader] We found a custom integration localtuya which has not been tested by Home Assistant. This component might cause stability problems, be sure to disable it if you experience issues with Home Assistant”
Nothing to worry about if that message is the message.
If it fails, then you need to look at other messages.
And to answer your second question: yes you can have both local tuya and cloud tuya working alongside each other. There is absolutely no issue with that and they will not interfere in any way. I have it setup like this for many months now.
However, you will need to create new device names. So every device will appear twice now in your home assistant configuration, one device linked to local tuya and another device linked to the cloud tuya integration. Both will be able to control the same physical device.
It is not so useful to do so, but you can. In the rare cases that local tuya acts up, at least all your devices can still be controlled via cloud tuya.
I guess if you really want to, you could write all your automations to check if the local tuya device is unavailable and if so, fall back to the cloud tuya device. But local tuya works so well I wouldn’t recommend to spend the effort 
thank you @tjafbe does this gives a hint ?2022-10-23 15:19:43.882 ERROR (MainThread) [homeassistant.config_entries] Error setting up entry localtuya for localtuya
File “/config/custom_components/localtuya/init.py”, line 242, in async_setup_entry
File “/config/custom_components/localtuya/discovery.py”, line 70, in datagram_received
File “/config/custom_components/localtuya/discovery.py”, line 79, in device_found
File “/config/custom_components/localtuya/init.py”, line 105, in _device_discovered
File “/config/custom_components/localtuya/common.py”, line 124, in async_config_entry_by_device_id