I was also almost a fan of AMD until buying laptop with Intel/AMD PowerXPress...
Of course this will not completely solve your problem, but try to use Gallium OpenCL SDK for opensource driver. Maybe it will work until your problem is not solved.
Although, I wold downgrade OS to the working version.
Thing is tho, I don't want to run two different versions of Ubuntu. I already have two other Ubuntu 16.04 LTS machines and one VM in my lab, all upgraded fine (They're Phenom II and Athlon II machines on nForce boards with NVidia GPUs, from the time before AMD bought up ATI- my lab consists mostly of this kind of machine). This machine I'm having trouble with was the first full-AMD machine I've ever built, and the GPU was specifically chosen to match the CPU so I can dual graphics the machine, but now it seems that there is no fully functional driver for the architecture.