Did you try a later kernel? out of the box ubuntu 16.04 is on the longterm 4.4 kernel. It looks like some ryzen features and patches have been added to 4.10, and they probably were not back-ported to the longterm kernels.
This sounds disturbingly unacceptable yet accepted
Having experienced first hand AMD driver instability on both Windows & Linux, AMD have lost my custom for the next 10 years..
Multiple re-occurring driver crashes using their main graphics card product line(RX380) on Windows 10.. So, pretty mainstream and yet having driver crashing (even when doing non-intensive tasks e.g. web browsing)
For the record, I'm not so sure Nvidia is any more stable either. The only (constantly) stable graphics provider over the years has been Intel's on-board graphics.
I installed the official AMD RX580 drivers and it's been stable since.