Today, I have posted a small guide how to configure OpenElec 5.x (RC2 is out at the moment) for the HiFiBerry Amp and Amp+.
If you want to use it with the DAC or Digi, you can use the same guide. Just remove the autostart script for the volume control and configure the right modules as shown in our configuration guide:
A generic OpenElec configuration guide can be found here:
OpenElec configuration guide