I'm on an EC2 instance. Most of the effort was on cuda/pytorch/pip nonsense. Once stable diffusion webui was working, diffusers worked basically out of the box, which was really nice. (Trickiest bit was figuring out that I needed to use their tool to convert my safetensor file and that the version of python I was using wasn't working with it for some reason). Stack is flask + gunicorn which was what chatgpt recommended (lol). I had a websockets version of the progress bar working on flask-socketio on my local machine but could never get the server version through nginx to work correctly. So eventually I just gave up and switched it to polling so I could launch.
