Well you can use Vulkan over Metal with MoltenVK, so that point is a bit moot.
Opinion time: WebGPU will become the standard graphics API to target for cross-platform. gfx-rs/wgpu already works over Vulkan/Metal/D3D12/D3D11/OpenGL/WebGL & WebGPU in browsers. Much better than simply Vulkan, unless performance is your primary sticking point.
Opinion time: WebGPU will become the standard graphics API to target for cross-platform. gfx-rs/wgpu already works over Vulkan/Metal/D3D12/D3D11/OpenGL/WebGL & WebGPU in browsers. Much better than simply Vulkan, unless performance is your primary sticking point.