Hello. Yes you are correct that it's not been tested (I don't have one). The iqaudio guys did actually recently reply regarding what was needed to support their latest boards but I must admit I forgot to implement it, apologies.
I think the problem is that their boards come up muted (I don't know why) and you need to end up with the following in /boot/config.txt for it to work properly:
I think this extra unmute_amp parameter might require some changes to our regular sound setup code. I'll look into fixing that tomorrow. In the meantime you should be able to edit /boot/config.txt manually and get it working. Hope that helps, looks like a cool card.