Ubuntu 20.04 keyboard media keys do not work
Solution 1:
I have found a solution to my media keys problem on Ubuntu 20.04.1
By default the Media Play button is not set on 20.04 out of the box.
Go to Settings → Keyboard Shortcuts and move down the list to the Sound and Media section and navigate down the list to Play (or play/Pause)
which will open the set key dialogue box
Once there, press the Home Page (WWW) button to set it and finish off by selecting Set