While HD44780 were quite well documented for RPi1, there is some confussion with RPi2/3 with LibreElec. In case you don't know them, HD44780 screens are affordable and easy to use displays that communicate over a parallel connection. They can be attached to an RPi on the GPIO directly, and they are excellent for displaying data without opening your monitor or TV.
With the latest LibreElec (v8) you will need to install the LCDProc add-on and the XBMC.LCDProc. The first one provides the driver, which used to be part of the LibreElec distribution up until version 7. The second one is the communication between Kodi and the driver.
Once you installed those, you need to place this config under .kodi/userdata/addon_data/service.lcdd/LCDd.conf
Pay attention to lines 146 to 151, you need to connect the LCD Pins to the GPIO as specified there.
Read more here: http://lcdproc.sourceforge.net/docs/current-user.html#hd44780-raspberrypi
and see the attached image for the wiring.