Hi, sorry for being late but as @Bhack mentioned, the Object Detection fine tuning story on TFHub is not perfect. Most of the OD models that were published don’t have the proper api to be fine tuned easily (like the image classification ones you mentioned)
Depending on the project you’re building, I’d suggest you try Model Maker (Object Detection with TensorFlow Lite Model Maker 16) as it’s the simplest solution you’ll find