DragonFly uses OSS for sound.
Load Intel HDA sound drivers on boot, add to /boot/loader.conf:
snd_hda_load=YES
Load all sound drivers:
kldload snd_driver
Display all sound devices:
cat /dev/sndstat
Installed devices: pcm0: <VIA VT1708S_0 (Analog 7.1+HP/2.0)> (play/rec) default pcm1: <VIA VT1708S_0 (Digital)> (play) pcm2: <VIA VT1708S_0 (Rear-panel Digital)> (play) pcm3: <NVIDIA (0x0042) (HDMI/DP 8ch)> (play) pcm4: <NVIDIA (0x0042) (HDMI/DP 8ch)> (play) pcm5: <NVIDIA (0x0042) (HDMI/DP 8ch)> (play)