The listed display works like a normal HDMI display, except that it communicates its horizontal pixel resolution as 1/3 of its nominal horizontal pixel resolution to the OS, then stretches the incoming image 3x horizontally. It also can only display grayscale values.

The image to display therefore has to be converted to grayscale and "squished" beforehand to display correctly.

This can be done with an image editor or a script, I use a python script.

The next step in this project is to find out if the display driver stretches the image via pixel triplication or actually distributes the RGB values of each pixel to three adjacent dots, like in a color display (which would make more sense). This would allow me to use the full resolution of the display by taking the grayscale values of three adjacent pixels in a greyscale image and put them in a single rgb pixel.