The codes have been updated with a lot of bugs fixed.

Basically I've overhauled the setup instruction and it's now reproducible with a fresh-installed Armbian Bionic 5.90. (I believe.)

I've also added some information about enabling the on-board Audio output.

Well, Since it's almost automatically configured by pulseaudio, what we have to do is:

# Enable `analog-codec` overlay
$ sudo armbian-config # [System - Hardware] or sudo vi /boot/armbianEnv.txt

# Create the simple ALSA config
$ cat - | sudo tee /etc/asound.conf
pcm.!default {
   type hw
   card 0 
}

ctl.!default {
   type hw
   card 0 
} 
# Ctrl + D
# Install pulseaudio (the daemon will be launched automatically when Xorg starts )
$ sudo apt install pulseaudio pulseaudio-utils pavucontrol

# Configure the audio settings as you like
$ DISPLAY=:1 pavucontrol # Launch pavucontrol in a VNC display at :1.
$ alsamixer