Well it seems that since Apple hasnt completely pulled the plug for OpenGL support, so that is still an option. And also Vulkan though not natively supported on Mac has an extension for Metal, MoltenVK, which allows Vulkan code to be used on Mac iirc.
If we were to actually do many different platforms, it seems like bgfx would be the solution, but I know it is criticized a lot, especially by core developers for not having direct access to the native APIs. But I’m not really into the idea of using Bgfx in the first place.