Maxime and I did a mountain of testing since ~June so the 8-bit side of his code is in great shape, but there are still milestones to achieve. The DRM driver that underpins everything is missing 10-bit capabilities so we're unable to fully test the HEVC parser code in the vdec and Maxime is still working on seeking (which is more about Kodi and ffmpeg than his vdec). There is currently no hardware deinterlace code (only software which is watchable but not brilliant) and we still need to persuade that and VP9 support into existence. On the positive, we have HDMI 1.4 (up to 4k30) working - although only for 2GB+ boards as Amlogic's alternative to AFBC isn't supported in the DRM driver yet so we're using too much RAM. The mainline kernel is also missing HDR support, but based on recent email exchanges with Intel staff we'll see some movement on that soon and we'll be able to hook into the same kernel frameworks. Kodi is also seeing some love in that area so at some point between K18 and K19 you'll be able to watch an HDR movie without having to force the colourspace and other dumb crap that doesn't work in older 3.14 kernel releases. We're also missing multi-channel audio support but the same Synopsys audio IP is used in a broad ranges of Amlogic, Allwinner and Rockchip hardware so there's a plan to pool efforts and collectively solve that at some point.
So right now if you only want 1080p or 4k 8-bit video + stereo audio it's pretty stable and usable. I'm not planning to start major public testing until after 9.0 ships and a few more pieces of the jigsaw come together - largely because I don't have the bandwidth for needy users and the support work that releases entail. I'm not sure if we'll jump to using lima immediately - it's not perfect yet (as that video shows) but that will come with time and love. NB: There's also been recent progress on the lowest-level boot code (ATF etc.) which is the final layer of closed-source Amlogic code to tackle. If that work completes it's indeed plausible that 2019 might see GXBB/GXL boards running a 100% open stack, which would be awesome and frankly rather amazing considering where things were a year ago.