We think Deepnote is a great tool to help you build or grow your community. As a community builder, you will get access to the Deepnote Team plan for free - you can invite the whole community, share projects, and collaborate together.
There is no definition really. It can be a general data science community for hundreds of members or a group of enthusiasts who like to play around with notebooks or a specific library (we ourselves are huge fans of plotly). An example is our own Deepnote community.
Create a new team and select the community builder plan - tell us about what you are building, we would love to help.