For my part, I wanted to get rid of Endomondo to keep my data on my own server. So I'm working on this personal project (to learn Python and React):
There is still a lot to do (see the issues 🙂) and for now I'm using an existing mobile app that stores the data locally, but it's a start.
And federation would be an great feature.
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!