Does AWS connect support SIP transfers natively?

Yes, AWS Connect does support SIP transfers natively through its external voice transfer feature. This capability allows Amazon Connect to integrate with other voice systems to directly transfer voice calls and metadata without using the public telephone network.

Regarding your specific use case of integrating AWS Connect with your own Natural Language Understanding (NLU) system, you can use Amazon Connect's external voice transfer feature to route calls to your server for NLU processing.

As for your concern about Chime SDK Voice Connector, there's no official information indicating that Chime will be deprecated soon. In fact, Amazon Connect continues to use Chime SDK components for various functionalities, including SIP-based integrations. The Amazon Chime SDK is still actively supported and used in conjunction with Amazon Connect for features like external voice transfers.

However, it's worth noting that for your specific use case of integrating with an external NLU system, you may not necessarily need to use the Chime SDK Voice Connector. The native external voice transfer feature of Amazon Connect should be sufficient for routing calls to your NLU system.

To set this up, you would need to:

1. Create a voice transfer connector in the Amazon Connect console.
2. Configure your on-premise voice system (in this case, your NLU server) with the voice transfer connector hostname.
3. Set up a flow in Amazon Connect to route calls to your external NLU system.

This approach allows for seamless integration between Amazon Connect and your NLU system without relying on potentially deprecated services. Amazon Connect's external voice transfer feature is a supported and forward-looking solution for integrating with external voice systems.

If you have any specific requirements that aren't met by this native functionality, it would be best to consult with AWS support or a solutions architect to explore the most appropriate and future-proof integration method for your use case.
Sources
Amazon Connect now supports external voice transfers - AWS
Configure the external voice system - Amazon Connect

Sounds like you want the call to ingress into your IVR (AI) and then go to Connect using a SIP trunk. If so, no the answer is no. Publicly this is not supported although it's possible that this is a feature that is coming.