Webrender (the new renderer maxyme was talking about) will move to gfx-rs later on [1]. That allows the renderer to run on Vulkan, DirectX 11 and 12, Metal and OpenGL.

[1] https://github.com/servo/webrender/issues/407

Since Firefox is a cross-platform project it'd be easier for them to target Vulkan and then use the MoltenVK library to do Vulkan on macOS:

https://moltengl.com/moltenvk/

https://www.khronos.org/vulkan/

Work on WebRender started before Vulkan API was widely available (even now there are lots of users, that can't use it) and right now they focus on integrating it in Firefox. Vulkan support is kept to be implemented "later", as it should enable further opportunities for parallelization in future.

Sadly a substantial number of Mac users are on os versions that don't support Metal. And a substantial number of then wouldn't even get support if they updated their OS.

So Metal-only isn't really an option for many projects, it's OpenGL + Metal or just OpenGL (for now).

That's a problem that Apple fabricated themselves. All MacOS games would also have to switch and I don't see that happening other than through the MoltenVK library if they support Vulkan at all.

Apple deprecated a lot of stuff decades ago that still works fine (talking about macOS).

There will be a free OpenGL-over-Metal implementation sooner or later, so I would still go with OpenGL for a cross-platform application.

That's Apple's problem, not Mozilla's.

Going to affect the LibreOffice guys also.

Apple caused it, but Mozilla (and, well, everybody else) needs to pay for it.