I'm very surprised Google put in so much effort to implement an approach that is basically the equivalent of client-side verification of passwords. Did no one designing it mention that it could be defeated by any rooted device?

I have a feeling Apple is going to knock it out of the park on this when they get around to it. They have a great foundation for doing image provenance well. The device attestation workflows are already there. And the same attacks that work against Android won't be as easy or effective because of Secure Enclave. Apple could run the whole signing process inside SEP.

And, Apple could choose to integrate a LiDAR depth map into the signed photo as a mitigation against the analog attacks (eg. pictures of screens).

I got a good laugh out of the "unblur to verify" first image. I dont know what I was expecting to see.

I would be interested in a note on whether Sony / Leica / Olympus “content credentials” do any better with their hardware to ensure a signature is assigned to data straight off the sensor.

I expect the only plausible chance (and it is a stretch) will be at-the-censor marking. Quantum bla bla magic pixie dust or unicorn farts something. The chance of a trustworthy (including from nation-state tampering a la Stalin et al) means of verification of digital anything is as good as dead imho.