They have a page about federation, in which they explain why they haven’t implemented federation yet.
In short: privacy concerns (e.g. metadata leakage), lack of devs / manpower & resources, difficulty adapting Revolts protocol to a federated one.
I like the project. I think it would be the perfect place for Foss Projects and a good replacement for Discord, but it is in dire need of more contributors and ppl, who know how to properly integrate Federation. I’d love to see Revolt succeed.
Currently I am short on time, but I’d love to contribute to them in the future.