NVIDIA/Radeon Windows 10 vs. Ubuntu Linux Relative Gaming Performance
With Shadow of Mordor, the Radeon/NVIDIA Linux gaming performance was roughly 70% the speed of Windows.
With minimum quality settings in Civilization 6, the Linux gaming performance ranged from ~30% with Radeon GPUs to ~60% with NVIDIA GPUs compared to Windows with the DX12 renderer.
With ultra quality settings, the four tested GPUs on Linux were at under 50% of their Windows performance.