I happily found Chromium-VAAPI almost 2 years ago and it works great with Intel integrated GPU video acceleration on Arch Manjaro Xfce
At least for AMD cards it works with no extra configuration. Besides installing the open-source driver if the distro doesn't do it automatically. I'm not sure which framework it's using VAAPI/VDPAU. My test method is: my GPU activity spike up when I hit play on a Youtube video. :) I'm on Arch/Gnome.
That's just not true. Might be a problem with some GPUs but not with all. At least I got hardware accelerated video playback on Chromium with my AMD GPU.