After much reading of basically every forum on the internet that consists of the function name vkEnumeratePhysicalDevices(), and after the week long bounty on this question still remained unanswered, I've found the answer. It lies within the interop between AMD and Nvidia drivers, at least for my laptop (ROG Zephyrus G14). The forum in which the answer was hiding was here:
https://github.com/KhronosGroup/Vulkan-Loader/issues/552
From what I understood from what they were saying over there on GitHub, what is happening as @pdaniel-nv describes, is the validation layers VK_LAYER_AMD_swichable_graphics and VK_LAYER_NV_optimus both want to pick High Performance GPUs, but they only want to filter for AMD or Nvidia GPUs respectively. (VK_LAYER_AMD_swichable_graphics wants to use AMD dedicated GPUs and VK_LAYER_NV_optimus wants to use Nvidia dedicated GPUs) So what happens is both drivers from AMD and Nvidia filter out each others GPUs when these layers are used so the list of available GPUs ends up with nothing.
So basically the solution is to disable one or both of those layers through Vulkan Configurator, or better yet in your code. The only downside is that the developer now has to write custom code to determine which GPU is optimal for their program—which honestly is no big deal in my opinion.
