> What concrete action would you propose that the Python core devs take at this point?

Nothing for now.

I stumbled across this issue through https://gitlab.kwant-project.org/kwant/tinyarray/-/issues/20 and had the impression that the aspect that I raised (that, for example, hash values of immutable built-in objects now no longer survive pickling) was not examined in this otherwise in-depth discussion.  So I added it for reference.

If problems come up that are caused by this change, I would consider reverting it a possible solution.

> The result of the change linked to this PR is that the hash now also reflects that containment depends on object identity, not just object value.

This is a nice way to phrase it.  Thanks for the link to the entertaining talk. :-)