E. K.

Thanks ioness! Exactly the info I was looking for.

Thank you for your input, much appreciated. It doesn't answer my question though, if Karma CPU runs without problems on Ryzen/Threadripper.
Since we are specifically discussing Karma and not RS/Octane a maybe higher performing Karma GPU CL implementation down the road is currently irrelevant as only Karma CPU is available. And my feeling is that Karma GPU is still far away.

W.r.t to GPU render engines I'm not in the “they are the holy grail of rendering” camp. GPU renderers have admittedly made big improvements in the last years. And while I like the speedy feedback of RS, when it comes to rendering smoke/explosions, vdb's, caustics it can't match Mantra's or Arnold's quality. In addition, when scenes become really big RS's speed advantage gets nullified.

twod
We try to remain as device-agnostic as possible by using OpenCL. Currently the denoiser is locked to Nvidia GPUs (as it's their denoiser), but we have plans to support other denoisers as well. As RobW mentioned, you should be able to run karma on both a GPU-less farm machine via CPU CL and a local workstation with GPU CL, without any user intervention. And if you're lucky enough to have farm machines with GPUs, you can use the GPU on both.
When the Karma GPU variant is released, of course

Will the soon to be released 4000series Ryzen/Threadripper CPUs even be viable for Karma CPU rendering? Without AMD CPU CL support my impression is that Karma wouldn't run at all. Am I wrong or would Intel CPUs be the only alternative then? Not my preferred choice with Intel's current performance and pricing.