Useful or not, from you.
absinthe Apollo Federation

Are there any plans on supporting Federation (https://www.apollographql.com/docs/apollo-server/federation/introduction/)?

That's a useful answer
Without any help

So is it not possible to leverage Apollo Federation while also using Absinthe Elixir ?

Mesh should, at least in principle, be able to add a Federation implementation to an existing nonconforming schema: https://www.graphql-mesh.com/docs/transforms/federation via https://github.com/0xR/graphql-transform-federation