A deep dive on how this new material works, way more advanced than how it looks from screenshots.

What prevents anyone to take a signed picture by photographing a generated/altered picture? You just need to frame it perfectly and make sure there are no reflections that could tell it's a picture of a picture and not a picture of the real world, very doable with a professional camera. All details that could give it out would disappear just lowering the resolution, which can be done in any camera.

So all I would have to do to make a "legitimate" fake picture is to generate it, print it, take a signed picture of the print with a camera and then upload it on the web?

With the right setup I could probably just take a picture of the screen directly, making it even easier (and enabling it for videos too).

Google "headless macbook", there is a community of people making macbooks without displays.

The idea started from recovering macs with a broken display and using them like a mac mini. It's possible to find "broken macs" for cheap in second hand market and if the problem is only the display you can go for the headless approach and have macOS with Apple Silicon for very cheap.

Apple Silicon has outstanding battery life, without a screen I would think even more.