My team are developing an app that will involve some on device ML model that are in onnx format. Currently we considering Flutter & React Native. I prefer Flutter but couldn't find any plugin that support running on device onnx model. in RN we could use onnx.js from Microsoft.
I think there is no Flutter Plugin to do this but you only need to create one in your project (link) and take implement Android version and iOS version. The plugin will make the wrapper and you can use it in your Flutter code. Depending of the phone OS, flutter will execute Android or iOS code.