Here are some settings specific for the Intel NUC.
The sound is propagrated through the HDMI. Install package alsa-utils.
Then set up the correct default card.
$ aplay -l **** List of PLAYBACK Hardware Devices **** card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1] Subdevices: 1/1 Subdevice #0: subdevice #0
Then you can set up ~/.asoundrc to load default card at user startup or use /etc/asound.conf for system-wide settings.
$ cat ~/.asoundrc defaults.pcm.card 0 defaults.pcm.device 7 defaults.ctl.card 0
Card needs to be set at 0 for the Intel NUC, device at 3 or 7 depending on the HDMI slot used. You can still find the speaker being used with command speaker-test. Test it before setting it!
speaker-test -D plughw:0,3 # for slot 1 speaker-test -D plughw:0,7 # for slot 2