Jupyter notebook isn’t a language, it’s a tool for running interactive sessions, in principle with any language. I’m fairly certain people run Julia in Jupyter Notebooks.

As for the advantages of Julia versus Python, arrays are native types, so they interface better across the entire language. It’s also shockingly fast in comparison, it compiles the code at runtime, so the longer the program runs, the faster it is.

If there is a use-case for R that Julia or Python can’t do, I haven’t seen it. I personally don’t see the point of writing code in R when the Python and Julia are more broadly useful to learn.