It specifically refuted lambda calculus as both minimal and rigorous due to the stipulation of code as data vs data as code. Nouns also being more general than lists.

sort of, in theory, but in most practical lisp/scheme implementations, certain values are opaque primitives. often functions are opaque. hashmaps, etc, are often primitives which don't have a "dependable formal representation". this means they cannot be e.g. serialized and coherently transmitted between processes.

Urbit solved this with nouns, which is arguably a substantial innovation. PLAN (in the author's view, which I find convincing) improves on this: https://git.sr.ht/~plan/plunder/tree/master/item/doc/PLAN.md

This looks really weird to me. I very much doubt this can be made into something practically useful.

Have you seen Unison[1]?

Unison seems like a much more interesting approach to making functions "serializable" and functional programming acquiring distributed capabilities almost transparently.

[1] https://www.unisonweb.org/

Hashed computations including functions distributed over something like DHT is a great concept with a lot of potential for a new form of computation.