This year we'll be using SMC (Sage Math Cloud) https://cloud.sagemath.com, recently renamed https://cocalc.com. CoCalc includes everything you need to code in the cloud. I think it's on GCP (Google Compute Platform) as opposed to https://repl.it, https://cs50.io and https://c9.io which are on AWS (Amazon Web Services). On Cocalc you can make 3 different types of documents: SAGE WorkSheet, Jupyter NoteBook and LaTEX Documents.