to run an AI engine on a device requires optimized code. Both IOS and Android on working on supporting AI engines natively, but the trained model will need to be compiled to the native engine.
so in practice you will build and train a model. then covert to model format supported by the devices you want to support. your will then build a native wrapper around these models, which is callable from Maui. You should be able to make the api similar for all platforms.
if you are using an already trained model, you might find it has cross platform support. as time goes on, these will become more available.