> effectively sidesteps the issue by making everything render to sRGB

Wow, that seems ... really unfortunate? So on macOS, if I open a nice photo from a friend that's tagged with AdobeRGB, Firefox will downconvert that to sRGB? I hope they don't bring that change to any other OSes!

You're right that mode 1 is flaky and could use some improvements (video, canvas elements, av1 which is treated as video by the decoder...) but converting wider gamut graphics down to sRGB seems like a clear step in the wrong direction.

By the way, Firefox passes all the tests in the article you linked to for me.