@youstones, hi, welcome to the forum!
You no longer need to use my fork, as the official and released version of Arduino_GFX now also supports these shields on both Arduino UNO R4 version. Available in Library Manager as GFX Library for Arduino.
Unfortunately, this library doesn't support read from displays, so you can't check for the controller used. And there are different controllers used and conflicting information:
Specification:
Option: with touch screen, without touch screen
Input voltage: DC 2.8~3.3V
Disc IC: ILI9486 / ILI9488L
Screen Size: 3.5 inches
Screen material: TFT
Resolution: 320x480
Pin Module: 28 pin (8 + 8 + 6 + 6)
Touch length Pen: 8.8cm/3.46in
Module size: 8.5 x 5.5 cm / 2.17 x 3.35 in
Weight: approx. 55g / 1.9oz
Driver IC ILI9486/ST7796
So you would need to try with different controllers.
If you have an Arduino UNO R3 (or any of the Atmega328 UNO versions), you could try with the library MCUFriend_kbv. It has an example to read the controller ID: LCD_ID_readreg.ino
(I would suggest to buy a classic UNO for such tests.)
-jz-