Just because a trichromatic screen has a large coverage gamut, such as Adobe RGB, doesn't necessarily mean it also has a high CRI. Emissive screens can use three fairly narrow color bands to fool our eyes and brain into thinking we see colors they are not actually emitting.

Typical output of an RGB emissive display.

Since the color filter arrays on digital camera sensors are NOT the same three colors as those used by our emissive displays, using a screen with low CRI (even having a large gamut) won't allow you to capture all of the colors in the negative (which has three dye layers that use another different set of three colors).

But I think restricting yourself to any kind of LED display is a bit of an X→Y problem. All you need is a well diffused high CRI light source.

Any high CRI light bulb behind a high diffusion screen will do the trick. A simple light baffle inside a reflective enclosure, such as a small "softbox" made to go on a camera mounted speedlight flash, should ensure even illumination on the screen at the front of such a diffuser. For that matter, a speedlight on low power works for many folks. Some even use a cyan gel to help offset the orange color of the film substrate with color films.

No fancy LCD is needed at all.