Currently, Mito only works in Juptyer Lab version 2.0. We don't work in either Jupyter Notebooks, Jupyter Lab 3.0, or Google Collab. However, we'd love to expand to those in the future.
Since we only support Jupyter right now, about half of the early Mito users are using it locally and the other half are using it on a hosted version of Jupyter Lab, which just makes it really easy to get setup without worrying about Python installations.