Exactly. This won't stop any determined bad actor, if anything, it's just going to boost their credibility when they inevitably come up with a bypass that allows them to sign any piece of media as "authentic" (in a few days or weeks after a device implementing such a scheme is released).

What then? 99.9% of honest actors are paying with their privacy[1] and usability again, while remaining 0.1% of dishonest actors are using a bypass - which sounds a lot like piracy and various DRM schemes. We've been here before, and it never works.

[1] While this might not be an immediate goal, I think it's pretty obvious any such scheme would eventually be corrupted to encode a traceable device ID into every photo and video taken with the device - to protect the children and stop CSAM, of course!

Hmm, how about watermarking the photo with some function of the OTP? (like bit steganography; invisible to normal human use)

Seems to preserve easy checking by device manufacturer, but not immediately clear to me how to replace the sensor in a way that gets a signed image.

And if it seems like a bit of trouble, I think it's still worth consideration by the manufacturer, as a feature for their images and support of a community of users who want to produce images that can be so validated