I bought a 3.5" TFT a while ago that was advertised as having an ILI9481 driver and touch screen. As is typical of Chinese vendors the display that arrived did not exactly match the advert photos and the PCB is marked as having an ILI9488 driver.
As I could not quickly get it going it ended up being put aside for many weeks until I could spare some time to investigate.
By trying various setups I found that it had an ILI9486 driver (so advert and PCB marking is wrong!) and needed quite slow write strobes so that the logic signals get through the 10K logic level protection series resistors on the back of the display. If the write strobe is too fast the display remains white even when the correct driver is used.
This is the display I have, the vendor advert has gone now.
To get a good performance with a Mega I have updated my library here so that it can be used with the ILI9486 driver. The library originally only supported HX8357B and HX8357C drivers hence the naming oddity. It also supports the ILI9481 driver.
The display now works fine
I haven't tried the touch screen yet but the display is fitted with an XPT2046 so this should be straightforward.