Hello @dzorlu,
Great to hear that you are working on a speech task!! Yes, the inference toolkit uses the pipelines from transformers. The code is open source you want to take a deeper look GitHub - aws/sagemaker-huggingface-inference-toolkit 2.
I am happy to share that we are working on new releases for the DLC, which include 4.9 and higher. Sadly I think it will take around 2 more weeks to be around.
In the meantime, you could use the official DLC and provide as model_data a model.tar.gz which contains a custom module, documented here: Deploy models to Amazon SageMaker 1
With a custom module, you can provide a requirements.txt to upgrade the dependencies and then provide a inference.py with a custom model_fn to load the asr pipeline.