I’d honestly choose a similar stack for the back-end. I have limited experience with Rust, but my impressions so far is that it’s a language that allows you to make changes with confidence that they’ll work. I feel like starting something in Rust is somewhat difficult, but contributing is relatively simple.

For the front-end, I don’t think the choice is as important, since I think that by virtue of being federated and being able to have multiple front-ends, it would almost be better for the front-end to be managed by other parts of the community. And I say that as a primarily front-end/developer-experience dev.