Birch also emphasizes IIT (Integrated Information Theory) claim that only consciousness exists intrinsically, while physical entities are extrinsic. With this, I agree that IIT approaches idealism, but not necessarily the kind that regards the physical world as largely an illusion, i.e., subjective or anti-realist idealism. It is more reminiscent of Russellian panpsychism (named after Bertrand Russell).

On the idealist version of this view, the physical world is fully real, but still fundamentally mental. The idea is that physical properties are purely relational or dispositional (“physics only tells us what things do, not how they are in themselves”, as it’s commonly put), whereas consciousness is intrinsic and can therefore be posited as the relata of all physical relations, or categorical grounds of physical dispositions. The view is also fairly similar to Leibniz’ monadology minus the claim that monads don’t interact.

https://philosophyofbrains.com/2023/...-part-iii.aspx