Oh, that's great to hear! I thought this might come into focus, once WebRender is officially released.

By the way, how is the progress for WebRender over Vulkan?

Current state of Vulkan port is that the correctness is on par with GL, minus a few driver bugs. We still need to re-architect WebRender a bit in order to get the performance advantage over GL.

I just switched to Firefox again after some shortsighted changes on Chrome. Neither give me GPU decode on Linux, but FF is SIGNIFICANTLY worse than Chrome on CPU decode. I can do a build in the background using all 12 threads and have no issues with video play back on Chrome (well, maybe not 4k60) but FF it's unwatchable, even at 900p60. (i7 8700k if you're wondering hardware wise, not OC'd because horrible chip and not worth it)

So VAAPI support can soon land in Firefox for Linux? Cool. This is great news for me.

Can you give us some details? When? Can I somehow help in testing, for example in Firefox nightly? What hardware can be supported? What formats, h264 or/and vp9?

We can't promise anything yet, sorry, but we are looking into it.