Hi @jcmoriaud and welcome to the Gladys universe.
For your question 1, I won’t be able to help because I don’t have any Tuya devices. However, I would be interested in your feedback in about a month (or sooner) to know whether you need to reactivate the Tuya APIs or not on the Tuya developer account. @Fabrice had issues (see his post )
For question 2, having a Thread key is not enough; you also need an OpenThread Border Router service, which is not yet available in Gladys.
There is a long post on this topic.
For your dongle, could you take a screenshot of the config in the zigbee2mqtt integration? (USB port and dongle selection)