See:

• DOC: add guide for downstream package authors numpy/numpy#18505
• REL: put upper bounds on versions of dependencies scipy/scipy#12862

The most important takeaway is that NumPy/SciPy now recommend downstream distributions to pin the upper bound version if NumPy/Scipy are runtime dependencies. (The example is if the latest NumPy out there is 1.20, one should pin to <1.23; the notation used in the docs <1.xx+3.0 is a bit confusing, see the clarification in scipy/scipy#12862 (comment).) There are other suggestions too, but I think this is potentially the most impactful one.