[mccoyb]

Have you explored the SciML landscape at all (?):

https://sciml.ai/

There are a number of components here which enable (what I would call) the expression of more advanced models using Julia's nice compositional properties.

Flux.jl is of course what most people would think of here (one of Julia's deep learning frameworks). But the reality behind Flux.jl is that it is just Julia code -- nothing too fancy.

There's ongoing work for AD in several directions -- including a Julia interface to Enzyme: https://github.com/wsmoses/Enzyme.jl

Also, a new AD system which Keno (who you'll see comment below or above) has been working on -- see Diffractor.jl on the JuliaCon schedule (for example).

Long story short -- there's quite a lot of work going on.

It may not seem like there is a "unified" package -- but that's because packages compose so well together in Julia, there's really no need for that.