The funny thing about GBM vs EGLStreams, though, based on everything I’ve read online, is that there’s broad agreement that EGLStreams is the technically superior approach - and that the reason it’s been rejected by the Linux graphics devs is GBM, while inferior, has broad hardware vendor support. Apparently very few GPU vendors outside the big 3 had decent EGl implementations.
That's not true. EGLStreams would be better suited to Nvidia's proprietary driver design, but it's technically inferior. This is the "broad agreement". No one but Nvidia wants EGLStreams, or we would have implemented it in other drivers.