I've been working on the #CoreML #StableDiffusion app over the weekend and it's at a fairly good point right now
Negative prompts, support for multiple models (you have to download them), multiple schedulers, a gallery of images generated etc. So looking pretty good if I say so myself
https://github.com/FahimF/swift-coreml-diffusers/
A few more things I want to fix but then it's time to see if I can add more (any?) features to the generator itself ...