I kinda solved the problem this morning, even if it isn't persistent for the moment...
1) Check that libreELEC "finds" the sound card : simple speaker test :
(plughw:0,0 is the default sound card, plughw1,0 is the Odroid DAC)
If you hear noise coming from the 2 speakers linked with your DAC, OK.
If not, the problem should still be in the modules that aren't loaded properly...
2) Make alsa load the module manually :
3) Choose the DAC in the Kodi audio settings :
This is only a temporary solution, but it works until reboot !
If somebody, could come up with a way to make it reliable, it'll be great