Realistically speaking, you probably should evaluate which path would bring you to your goal faster: converting pytorch to onnx and then to tflite micro route or using less known and maintained project to run onnx model directly.

Indeed, I am currently looking at the onnx based tools. Architecture aware training is of course also quite important, not sure how to cover that yet.

Since you mentioned Edge Impulse, why would you want to go self-hosted OSS route?

Well, first of all this is meant as a learning exercise for me, so I would like to be in control of every step. And then it is probably general mistrust vs. SaaS.

I updated the posting with some of my findings.