For those interested in continuing the __numpy_ufunc__ saga, there is a pull request enabling it. Likely we will want to make some changes up front before merging that, so some discussion is in order.
As a first order of business, let's decide whether to remove the index and rename `__numpy_ufunc__`. The motivation for this is discussed in issue #5986.
If we decide positive on that (I'm in favor), I would be happy with the proposed name `__array_ufunc__`, although something more descriptive like `__handle_ufunc__` might be better. This is a wonderful opportunity for bike shedding for those so inclined ;)