Ultimately, I was able to figure out this one by myself - but it was not straight forward to get to the root cause. As others had identified, tensor flow was the issue that was causing the problem, and it was that it specifically required AVX to be running on my system. I do have a modern Intel based laptop that does support AVX, but the issue is that I’m running inside a hosted VirtualBox environment, running my Rasa implementation as a Ubuntu image – and VirtualBox has an issue where it suppresses the AVX capabilities on systems where the host is running Windows, using Hypervisor services. Turning off Hypervisor in Windows 11 ultimately ended up being a fruitless effort, so I gave up trying to get VirtualBox to work properly.
Instead, focused on finding a version of TensorFlow that didn’t require AVX – and was able to find several references to a special build of TF that could run on these older machines. python - Run TensorFlow 2.0 on CPU without AVX - Stack Overflow
Once I was able to install a complete working stack, but replace out just the Tensorflow bits with these modified build, it worked. I suspect that it may not perform as well as the AVX version, but for the purposes of my evaluation it is working find.