Comment by adrian_b

For the kind of things needed by Firefox, the Linux APIs have been stable for decades.

The problem is not stability, but the fact that there are multiple APIs, and it is unknown which of them will be available on the user system, so a browser may need to support all of them.

For instance, for video decoding on a GPU, the Linux APIs differ depending on the GPU vendor, unless you use Vulkan, but Vulkan video decoding is not available in old computers. Even so, Firefox could have used some higher-level API that takes care of the low-level GPU-dependent details (e.g. ffmpeg).

More baffling is the failure of Firefox to use OpenGL or Vulkan for implementing WebGL, depending on the GPU vendor, because at least the OpenGL API has not changed in a very long time. I have no idea which is the reason (because Firefox does not provide adequate error messages), unless they depend on some vendor-specific OpenGL extensions. I use an NVIDIA GPU, on which I cannot enable WebGL in Firefox, despite the fact that WebGL works fine in Vivaldi and Chromium/Chrome and I use a very great number of OpenGL and Vulkan applications, including some written by myself, all of which work perfectly, with no problems whatsoever.