Pirate Audio - GPIO 20 and i2s

I am trying to help someone who has the Pirate Audio device (with mini screen and speaker) but wants to run it on something other than Raspbian (and not with Mopidy).

He has everything working apart from the volume up button on GPIO20.

The error he is getting implies to me that he cannot use GPIO20 for input rom the pin while it is also being used as part of the i2s subsystem used by the amp.

Is there something magic that allows this to work in the standard Pimoroni set-up?

I’m having similar problems. I’m attempting to map the buttons using dtoverlay=gpio-keys. Three map fine, but if i attempt to map the bottom right one, snd-bcm2835 fails to load, which the sound driver requires.