Ok, this is probably a niche use, but I’ve been wanting to mirror output so that it goes both to SmartMatrix and a TFT. This allows me to look at the generated output on the TFT if the RGBPanels are not plugged in, or not easily visible from the controller side.
If that is of any interest to you, you can look at Marc's Blog: arduino - FastLED_ArduinoGFX::TFT on top of Framebuffer::GFX for SPI TFTs like SSD1331 or ILI9341
That driver, and the new multi-device neomatrix_config, allows you to have multiple output devices, each with their own framebuffer, or sharing the same framebuffer (which then mirrors the output)
I didn’t have the right hardware on hand when I did the demo (TFTs are much easier to carry in a plane, haha), but here is an example of multi framebuffer:
Obviously the 2nd display can be a smartmatrix instead.