Shame though that by the time you've gotten your first cross-platform triangle on screen in Vulkan you'd already be finished covering Windows and macOS via D3D1

Shame though that by the time you've gotten your first cross-platform triangle on screen in Vulkan you'd already be finished covering Windows and macOS via D3D11 and Metal, and with fewer total lines of code ;) (D3D11 is not a typo, unfortunately D3D12 isn't that much better than Vulkan in that regard)