I have made some heavy modifications, as the typical Adafruit TFT libraries are designed to work with 16bit color (RGB565), and the ILI9488 can only do 24bit (RGB888) color in 4 wire SPI mode.
It is based heavily on the Adafruit_ILI9341 library and is designed to work with the Adafruit_GFX library.
This library is for support for the 320x480 tft controller over 4 wire SPI.