If the purpose is to demonstrate a viable website, I'd go with Heroku, as the fundamental ideas of getting up and going, and iterating quickly on your idea, and continuously delivering your updates is pretty much handled for you. Heroku is amazing for developer experience, and while costs may scale differently than other solutions, the trade-off is in your time to develop and deliver the product.

I love Heroku for ease of Deployment but it gets very expensive as you scale. Digital Ocean is great for your purposes as others have said on here. The beauty of Heroku is the Dyno architecture, but really you can do this yourself by installing docker (free edition), it will save you a lot of money and you will need it as you get started. The tutorials on DO are all very well written, and Docker even has an Image for running GPU in a containerized Jupyter environment should you want that. https://github.com/iot-salzburg/gpu-jupyter/