So I raised a ticket (ticket no: [8200756636]) with AMD for this to be fixed and they responded with ...
" Thank you for your Email. I understand that you are observing blue screen issue when installing the sixth RX 580 GPU on your computer running Windows 10 OS. And you wish to know if blue screen issue with multiple RX 580 GPUs is been fixed. Yes, with the latest drivers with the multiple RX 580 graphics card in PCIe riser card on a single system has been fixed with the latest 17.6.2 Relive Edition driver. Please try installing the latest drivers on your computer and let me know the issue status. Perform clean driver installation using DDU utility tool Thank you for contacting AMD "
Just thought I'd share the hope that many of us are still chasing of a driver fix and see if anyone has already tried this new driver/installation so I can re-escalate accordingly if required :) I’m at work so can’t do this currently, but will be confirming tonight anyhow.