How to create a "Fallback intent" for everything not in nlu?


I want to use Rasa only as an intent classifier for a specific project, don’t need the utterances, actions, etc.

The only thing I’ve found so far is this question on the forum, which doesn’t have the answer: Rasa never send Fallback Intent on NLU response - Getting Started with Rasa - Rasa Community Forum

I want to have an intent that captures any text not listed in nlu training for other intents, is this possible?

Thanks in advance!