Similarly a client that just "does" HATEOAS and could be usefully used on any API is pretty much unattainable. At best you're going to be operating like a crawl

Similarly a client that just "does" HATEOAS and could be usefully used on any API is pretty much unattainable. At best you're going to be operating like a crawler. Knowing what to actually do and what's useful and what the resources and their components actually mean, that's all out-of-band, much like knowing the structure of a site you want to scrape.