I've install Kubuntu 17.04 on Dell Vostro 5568 with encrypted filesystem. The laptop comes with UEFI bios. In order to install nvidia drivers I had to disable secure UEFI boot. After turning laptop off and on again the sound card stopped working. The whole hard drive is on encrypted LVM.
$ lspci -v | grep -A7 -i "audio"
00:1f.3 Audio device: Intel Corporation Device 9d71 (rev 21)
Subsystem: Dell Device 0786
Flags: bus master, fast devsel, latency 32, IRQ 16
Memory at d5228000 (64-bit, non-prefetchable) [size=16K]
Memory at d5200000 (64-bit, non-prefetchable) [size=64K]
Capabilities: [50] Power Management version 3
Capabilities: [60] MSI: Enable- Count=1/1 Maskable- 64bit+
Kernel driver in use: snd_hda_intel
$ 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
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]
Subdevices: 1/1
Subdevice #0: subdevice #0
Currently the only audio output device is "Dummy output". Funny enough after suspending laptop to hibernation and waking it up the sound card device appears correctly:
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC3246 Analog [ALC3246 Analog]
Subdevices: 0/1
Subdevice #0: subdevice #0
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
card 0: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]
Subdevices: 1/1
Subdevice #0: subdevice #0
I'm a bit suspicious about the combination of encrypted filesystem and UEFI boot that might cause problems with detecting hardware.
$ cat /proc/asound/card0/codec* | grep Codec
Codec: Realtek ALC3246
Codec: Intel Kabylake HDMI
Alsa manual does not explicitly state that Realtek ALC3246 card is supported but as the card sometimes works and sometimes there's no sound device at all I'm not sure whether it's still a software issue.
EDIT: After reboot the sound card is gone again. I've tried disabling and enabling sound card in BIOS without any success.