Feral Interactive have just announced some exciting news! The Linux port of Dawn of War III [Steam, Feral Site] will come with OpenGL as the default, but like with Mad Max you will be able to check a box to enable Vulkan! On Linux, the game will launch with OpenGL by default. However, an option to play using the Vulkan graphics API will be available via the Feral pre-game options window.
See https://www.gamingonlinux.com/articles/feral-announce-that-dawn-of-war-iii-will-use-both-opengl-and-vulkan.9739 
Feral announce that Dawn of War III will use both OpenGL and Vulkan
Feral Interactive have just announced some exciting news! The Linux port of Dawn of War III will come with OpenGL as the default, but like with Mad Max you will be able to check a box to enable Vulkan!