Also, note that C2PA should have something like Level 3 as well: "The image is mathematically proven to have come from the physical camera sensor."
It's somehow difficult to achieve this, but it's possible (although the attacks will always be possible of course).
But yeah, difficult too :)
The screen is doing all kinds of crazy things that are not apparent to your eyes, but that show up clearly on camera.
For example, you'll see a sort of barber-pole effect when pointing a video camera at a raster-scan digital display whose refresh rate isn't synced to the camera's frame rate. To avoid that, sync them, or maybe use a colour e-ink display.
Alternatively, print a high-resolution version with a decent photograph printer and take a picture of the print with the C2PA camera.