Total War: WARHAMMER was released this past May for Windows while the Linux port arrived in late November. This turn-based strategy game was ported to Linux by Feral Interactive. Under Windows there is Direct3D 12 and 11 renderer options while on Linux is just OpenGL.
With low image quality settings, the Linux OpenGL results weren't too much slower than Windows! Their beta DX12 renderer was also slower than the default DX11 renderer.
Even when running Total War: WARHAMMER at ultra image quality settings, the results weren't too much slower with Ubuntu Linux than the Windows results.