Vulkan Video is about exposing the GPU's hardware encoding/decoding functionality through the standard Vulkan API, not about implementing the codecs through shaders.

There are fairly mainstream devices with decent Vulkan support but poor hardware decode coverage for the codecs people actually get on the web. Polaris era Radeons have H.264 and HEVC decode, but VP9 support is absent (or not exposed in many common Linux paths) so YouTube is sloppy. The Raspberry Pi 5 is another example: it has hardware HEVC decode, but YouTube 4K is generally VP9 or AV1 rather than HEVC, and Pi 5 does not advertise VP9 hardware decode.

It doesn’t mean anything for desktop users, it’s just a new standard that could have wider support than VAAPI since it’s part of Vulkan. Mostly embedded devices lacking VAAPI support today, though nvidia requires a third party implementation so this might improve that situation.

Look at the post. It's already using ffmpeg. This just enables it in the build.

It should be, unless there are new issues. This code change landed in Firefox 153 Nightly and 153 will become the next ESR version (July 21).

https://whattrainisitnow.com/release/?version=esr