@screamingcities, the Adafruit RA8875 library looks very easy to port. The only problem with this device is:
Please note! The RA8875 does not tri-state the MISO pin, it should not share that pin with any other SPI device (including an SD card reader) without the use of a 74HC125 or similar.
The RA8875 is not compatible with the mfGFX library since it has its own built-in fonts and supports external font ROMs. It also supports 255 8x16 downloadable user-defined fonts/symbols in CGRAM. This allows symbols and/or characters to be downloaded to the display and then used as a font on the screen. The Adafruit library would have to be modified to support this. Also, the CGRAM is not persistent so the fonts/symbols need to be loaded every time the display is powered. That means a 4080 byte flash requirement on the Core to store all 255 8x16 cells.
The GFX and mfGFX libraries are designed for "dumb" controllers where the processor draws the fonts and graphics. In theory, an extra set of functions could be written to support mfGFX fonts on the RA8875, bypassing the display's "intelligent" controller and simply drawing them as pixels. 