Ubuntu – No sound with Ubuntu 20.04 on Asus Zenbook UX533FTC

I installed Ubuntu 20.04 on my new Asus Zenbook UX533FTC-A8178T laptop coming with Windows 10, in dual boot.

No sound comes out from the speakers, or the headphones jack (while in Windows sound is ok).

I previously tried with 18.04 and it didn't work either. For several days I browsed similar "no sound questions", but it didn't work out.
So now I freshly re-installed ubuntu 20.04, updated it, and installed pavucontrol, and inxi only for a fresh start.

Hoping someone can help I put some useful information below.

Thanks, Filippo

(PS I tried manjaro-gnome-19.0.2-200312-linux54.iso, while with Ubuntu 18.04 I tried different kernels: 4.19.0, 4.19.10, 4.19.43 etc etc)

• uname -a

Linux ZenBook 5.4.0-26-generic #30-Ubuntu SMP Mon Apr 20 16:58:30 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

• alsamixer

AlsaMixer v1.1.3 ────────────────────────────────────────

│ Card: HDA Intel PCH                                                                   
│ Chip: Realtek ALC294                                                    
│ View: F3:[Playback]                                                                        

Everything is on, "OO", Auto-Mute is disabled

• inxi -SMAG

System:    Host: ZenBook Kernel: 5.4.0-26-generic x86_64 bits: 64 Desktop: Gnome 3.36.1 
           Distro: Ubuntu 20.04 LTS (Focal Fossa) 
Machine:   Type: Laptop System: ASUSTeK product: ZenBook UX534FTC_UX533FTC v: 1.0 
           serial: <superuser/root required> 
           Mobo: ASUSTeK model: UX534FTC v: 1.0 serial: <superuser/root required> 
           UEFI: American Megatrends v: UX534FTC.304 date: 12/16/2019 
Graphics:  Device-1: Intel UHD Graphics driver: i915 v: kernel 
           Device-2: NVIDIA TU117M [GeForce GTX 1650 Mobile / Max-Q] driver: nouveau v: kernel 
           Display: x11 server: X.Org 1.20.8 driver: nouveau resolution: 1920x1080~60Hz 
           OpenGL: renderer: Mesa Intel UHD Graphics (CML GT2) v: 4.6 Mesa 20.0.4 
Audio:     Device-1: Intel driver: snd_hda_intel 
           Sound Server: ALSA v: k5.4.0-26-generic 

• pavucontrol

Output devices: Built-in Audio Analog Stereo
Port: Speakers (on which I can see the audio bar moving when playing a youtube video)
Configuration: Analog Stereo Duplex/Analog Stereo Output (same thing)

• cat /etc/modprobe.d/alsa-base.conf

# autoloader aliases
install sound-slot-0 /sbin/modprobe snd-card-0
install sound-slot-1 /sbin/modprobe snd-card-1
install sound-slot-2 /sbin/modprobe snd-card-2
install sound-slot-3 /sbin/modprobe snd-card-3
install sound-slot-4 /sbin/modprobe snd-card-4
install sound-slot-5 /sbin/modprobe snd-card-5
install sound-slot-6 /sbin/modprobe snd-card-6
install sound-slot-7 /sbin/modprobe snd-card-7

# Cause optional modules to be loaded above generic modules
install snd /sbin/modprobe --ignore-install snd $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-ioctl32 ; /sbin/modprobe --quiet --use-blacklist snd-seq ; }
#
# Workaround at bug #499695 (reverted in Ubuntu see LP #319505)
install snd-pcm /sbin/modprobe --ignore-install snd-pcm $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-pcm-oss ; : ; }
install snd-mixer /sbin/modprobe --ignore-install snd-mixer $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-mixer-oss ; : ; }
install snd-seq /sbin/modprobe --ignore-install snd-seq $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-seq-midi ; /sbin/modprobe --quiet --use-blacklist snd-seq-oss ; : ; }
#
install snd-rawmidi /sbin/modprobe --ignore-install snd-rawmidi $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-seq-midi ; : ; }
# Cause optional modules to be loaded above sound card driver modules
install snd-emu10k1 /sbin/modprobe --ignore-install snd-emu10k1 $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-emu10k1-synth ; }
install snd-via82xx /sbin/modprobe --ignore-install snd-via82xx $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist snd-seq ; }

# Load saa7134-alsa instead of saa7134 (which gets dragged in by it anyway)
install saa7134 /sbin/modprobe --ignore-install saa7134 $CMDLINE_OPTS && { /sbin/modprobe --quiet --use-blacklist saa7134-alsa ; : ; }
# Prevent abnormal drivers from grabbing index 0
options bt87x index=-2
options cx88_alsa index=-2
options saa7134-alsa index=-2
options snd-atiixp-modem index=-2
options snd-intel8x0m index=-2
options snd-via82xx-modem index=-2
options snd-usb-audio index=-2
options snd-usb-caiaq index=-2
options snd-usb-ua101 index=-2
options snd-usb-us122l index=-2
options snd-usb-usx2y index=-2
# Ubuntu #62691, enable MPU for snd-cmipci
options snd-cmipci mpu_port=0x330 fm_port=0x388
# Keep snd-pcsp from being loaded as first soundcard
options snd-pcsp index=-2
# Keep snd-usb-audio from beeing loaded as first soundcard
options snd-usb-audio index=-2