I wonder how they took pictures with four different cameras from the exact same position at the exact same point in time. Maybe the chameleon was staying very still, and maybe the flowers were indoors and that's why they didn't move in the breeze, and they used a special rock-solid mount that kept all three cameras perfectly aligned with microscopic precision. Or maybe these aren't genuine demonstrations, just mock-ups, and they didn't even really have a chameleon.

They didn't really have a chameleon. See "Experimental setup" in the linked paper [emphasis mine]:

> After fabrication of the meta-optic, we account for fabrication error by performing a PSF calibration step. This is accomplished by using an optical relay system to image a pinhole illuminated by fiber-coupled LEDs. We then conduct imaging experiments by replacing the pinhole with an OLED monitor. The OLED monitor is used to display images that will be captured by our nano-optic imager.

But shooting a real chameleon is irrelevant to what they're trying to demonstrate here.

At the scales they're working at here ("nano-optics"), there's no travel distance for chromatic distortion to take place within the lens. Therefore, whether they're shooting a 3D scene (a chameleon) or a 2D scene (an OLED monitor showing a picture of a chameleon), the light that makes it through their tiny lens to hit the sensor is going to be the same.

(That's the intuitive explanation, at least; the technical explanation is a bit stranger, as the lens is sub-wavelength – and shaped into structures that act as antennae for specific light frequencies. You might say that all the lens is doing is chromatic distortion — but in a very controlled manner, "funnelling" each frequency of inbound light to a specific part of the sensor, somewhat like a MIMO antenna "funnels" each frequency-band of signal to a specific ADC+DSP. Which amounts to the same thing: this lens doesn't "see" any difference between 3D scenes and 2D images of those scenes.)

Given the size of their camera, you could glue it to the center of another camera’s lens with relatively insignificant effect on the larger camera’s performance.

Camera rigs exist for this exact reason.