I have an HDMI 800x480 touch screen for the raspberry pi labelled "5inch HDMI LCD V2", which specifies that it has an XPT2046 Touch Controller. I was having difficulties getting the touch controller to work together with Ubuntu 'classic'.
Most tutorials to get the device to work simply specify that all you have to do is add the following to `/boot/config.txt`:
dtparam=i2c_arm=on dtparam=spi=on dtoverlay=ads7846,penirq=25,speed=10000,penirq_pull=2,xohms=150