Interestingly, some motherboards fare worse than others. Larabel speculates some issues may be caused by differences between the pre-production and the final launch hardware/software:
Open-source AMD developers have been working on the Raven Ridge support going back to last year and all. Thus I'm thinking some motherboard vendors with their BIOS updates changed some behavior adversely affecting the Linux driver support and/or the pre-production bring-up of Raven with the Linux driver stack is a lot different than what ended up being with the production hardware/BIOS... Perhaps this is why AMD hadn't offered any review samples this time around for our Linux testing or even briefed on the launch.