Vulkan clear color is wrong
This looks like the VkFormat being selected for the VkSurfaceFormat, most likekly VK_FORMAT_R8G8B8A8_SRGB. Try VK_FORMAT_R8G8B8A8_UNORM for the VkFormat with a corresponding colorspace (like VK_COLOR_SPACE_SRGB_NONLINEAR_KHR). That should give the dark color you are expecting.