Noob question: There's a way to write a OpenGL drive that uses Metal underneath?

The same company which originally built MoltenVK built MoltenGL for specifically this purpose.

https://moltengl.com/moltengl/

Awesome! Maybe some company like that could offer their driver for free to blender community, as a marketing strategy. I believe that even have some space to a sector giant (like autodesk) acquire this type of company.

It's probably possible yes.

I don't know if one already exist for OpenGL, but for Vulkan there's MoltenVK: https://github.com/KhronosGroup/MoltenVK