The later Milhouse LibreElec 9 for Kodi 18.2 (Generic) test builds using Linux 5 have ALSA problems on NUCs (no Passthrough Audio). I’m hoping this will resolved with official LibreElec 9.0.2 build.
I’ve had to stay with last Milhouse LE build using Linux 4.19 to use Passthrough.
Which Milhouse build ar you running for passthrough and what NUC hardware are you running ? I am struggling with bitstream passthrough on a NUC 8.