Since before Rescript was Rescript, I have shipped a number of production DDD services in the ReasonML/Bucklescript/Rescript world.
Unfortunately, I am not aware of any really great resources. As you have mentioned, ‘Domain Modeling Made Functional’ and all of his articles, are probably the closest things I’ve found, but it intentionally keeps things super simple, which does not necessarily scale to most systems that are big/complicated enough to benefit from DDD.
Functors are extremely useful for design, and separating models/ideas, isolating complexity. If you are just writing UI-layer code (which I believe is the majority of user-land Rescript), then it isn’t as useful. I think that is why we don’t see a lot of functor use/discussion in Rescript
But in my experience, if you are following DDD, functors are nearly irreplaceable as a design tool. For example, take repositories. The design of a repository is part of the domain design. It belongs in the domain layer. But the implementation of a repository is purely technical and belongs outside of the domain. IMO, the best way of those two things practically living in one system, and being properly disconnected, is as a separate module type and module, which are connected using a functor.
The best thing I personally did was to just read a ton of OCaml code (especially mirage-os code and systems built using it).