I was pretty active in the Raspberry Pi community around 4 years ago. Playing YouTube easily was a big problem and I tried making a lot of packages to solve this. I would also build Chromium to add widevine support for DRM content.

I also helped the Raspberry Pi Foundation around 4 years ago building and packaging their patched version of Chromium. What they essentially did was directly modify the Chromium source to add HW decoding specifically for the Pi with MMAL. Then, an extension would be auto installed to enable H264 on YouTube instead of VP9. This was released back when they launched the Pixel desktop.

This obviously had some problems, because the patch needed to be manually changed for every release of Chromium, which come pretty often. It couldn't also be easily upstreamed. Looking at it now, it seems it hasn't been updated in about a year, and I'm curious what the Foundation's roadmap for this is in the future, after having been out of the loop for so long.