And this is what all ontologies ultimately have to explain, physicalism only seems attractive because it provides a solid explanation of how this works, however, it utterly fails in explaining how consciousness arises from the physical and thus cannot be a correct account. Because of this, we now have some other options: neutral monism (sometimes called dual aspect monism), panpsychism, idealism, dualism, and some form of pluralism (more than two ontological primaries). The suttas don’t take a hard stance on these options, though I think one can rule out dualism.
This is generally termed Objective Idealism. Of course, you can have non-theistic accounts of this view, as well as more process based accounts of it. So I would not immediately rule out all options. A world mind need not be eternalistic and unchanging, it could be like a constantly changing ocean of mentatal processes, Schopenahuer’s Will comes to mind, or some interpretations of Nietzsche’s Will to Power.
This is the other idealist option, sometimes called “subjective” idealism. It’s an interesting view, but I think it has issues, because it seems like the external world is there whether or not there are minds thinking about it. After all, the universe existed for aeons before sentient beings arose. Of course, this theory is itself an abstraction which sentient beings came up with themselves, but its empirically supported. Also, one could at least conceive that there are universes without sentient beings, how are these possible? Indeed, the issue is so serious, that subjective idealists like Berkeley often have to posit a God to support the external world.
I think then that the most parsimonious explanation is that the universe is just a field or ocean of experience (which is not-self and always in flux). Physical objects and beings are just the congealed, individuated or hardened forms of these conscious patterns. This view is not alien to ancient India of course and can be seen in the Upanishads which influenced early Buddhism (and perhaps is referenced in some suttas, like Agañña). Of course, a Buddhist version of this would not be eternalistic or see the world mind as a God or as pure bliss and so on.
So far as I can see, all of this needs to be taken into account if we are going decide on the relationship between mind and matter. In the end, we might be better off leaving those leaves on the forest floor.
I am certainly sympathetic to this agnostic position, and it has been my position for some time. The reason I have recently changed my mind a little bit on this is that I have begun thinking how its possible that physicalism / materialism managed to become such a dominant force in our world. I think its because they were able to appropriate the mystique of the power of the physical sciences to explain the external world and make it seem like their metaphysics is allied with this (protip its not, its just a metaphysical interpretation of the scientific data). This is why I think I had such a hard time accepting rebirth and karma, and it was a huge obstacle for me. I think that providing a probable and rational metaphysics can help some people overcome that mystique. Now, I am not saying whatever metaphysics we come up with should be some absolute doctrinal view. It would just be a skillful way of saying: look, physicalism is just one metaphysical theory, and its not the best one either. There are other ways to interpret the world which are even better and which easily allow for karma and rebirth.
We just don’t live in ancient India anymore, our intellectual culture as it is at the moment is dominated (though this is slowly changing again) by physicalist presuppositions. So I am not sure if leaving all the same leaves the Buddha left on the forest floor is as skillful right now. That doesn’t mean we have to pick them up, but maybe we can lean down and take a peek and this might help with right view.