The TTGO T-display
Uses only 7 of the possible 10 touch pins as those pins are used for the display(T0, T1 and T6)
T2 uses GPIO pin 2
T3 uses GPIO pin 15
T4 uses GPIO pin 13
T5 uses GPIO pin 12
T7 uses GPIO pin 27
T8 uses GPIO pin 33
T9 uses GPIO pin 32
Example use touchRead(T3)
touchRead(T3) will read the GPIO pin 15 capacitance returning a value normally between around 80(not touched) to around 10(touched).
The issue with using this is it can give false reading, One solution can be to average a few reads separated by a short delay to make sure it is a finger touch as apposed to a false noise value returned.