DCS World runs on DirectX11 and at some stage they will begin development on DCS World 3. Switching to Vulkan at this stage would improve performance and make cross compatibility that much easier, maybe even a console variant like Flaming Cliffs 4 or something.
Also "anti windows crusade" is not misplaced, the bloatware, tracking, constant updating, security issues etc are all well documented and its users deserve better.
Sure Linux has issues (software support and some hardware) there is no denying that, but at least it gives a damn about the people who use it, and it is only getting better. When you use Windows you are the product.