Hi,
The semantic segmentation model is TensorFlow-based UNet.
The .uff file of the converted model is located at /opt/nvidia/deepstream/deepstream-4.0/samples/models/Segmentation/semantic/
You can find some training / re-training / inferencing information on our NGC model page:
https://ngc.nvidia.com/catalog/models/nvidia:unetindustrial_for_tensorflow_16
Thanks.