Hi @Gregorio96,
This problem has already been answered in this forum post: ERROR Keras Network Learner 0:14 Tensor is unhashable if Tensor equality is enabled. Instead, use tensor.experimental_ref() as the key.
KNIME currently does not support TensorFlow 2. Please make sure to have Keras 2.1.6 and TensorFlow 1.8.0 installed in your Python environment instead. Please refer to this installation guide to learn how this can be done directly within KNIME.
Marcel