Please elaborate more. I'm writing this from my Dell XPS 9575 with Vega M GL under Fedora 30 and I haven't encountered a single problem in GPU-accelerated applications and games with official open source drivers.
To add to this, the AMD OpenGL windows drivers are notoriously bad, whereas the Linux OpenGL drivers perform closer to DirectX. Performance on that end is significantly ahead.
Please elaborate more. I'm writing this from my Dell XPS 9575 with Vega M GL under Fedora 30 and I haven't encountered a single problem in GPU-accelerated applications and games with official open source drivers.