LSC Smart Connect Dimmerswitch does not connect to Local Tuya - "An unknown error occurred. [Errno 111]"

Hi all,
I just wanted to inject that into a discussion.

I have several Tuya devices in my HA System. All in all it was easy to install them. Only a dimmer device does not connect.
It is connected to the local network. I have the device ID and the local key. When trying to “add a new device” it is not listed by it’s ip. Also it does not show up when using the cloud API account, but I can see it in the tuya developer platform.

Adding the device manually results in “An unknown error occurred. [Errno 111] Connect call failed (‘192.168.178.241’, 6668)”

[More information can be found on github]([Bug]: LSC Smart Connect Wall Dimmer does not work with Local Tuya: An unknown error occurred. [Errno 111] Connect call failed · Issue #526 · xZetsubou/hass-localtuya)

Does anybody have an idea?